Chemistry important questions for CTEVT Certificate/Diploma Level first year in Health Sciences : General Medicine(HA), Medical Laboratory Technology(MLT), Diagnostic Radiography, Homeopathy, Ayurveda, Amchi Science, Dental Science, Ophthalmic Science, Pharmacy, Physiotherapy and Acupuncture, Acupressure & Moxibustion.

SET A: Lab preparation of:

i. Chloroform (trichloromethane)

ii. Nitrobenzene

iii. Aniline

iv. Ethene ( ethylene)

v. Ethyne (acetylene)

vi. Diethyl ether (ethoxy ethane)

SET B: Lab preparation of:

i. Carbon monoxide   ii. Ammonia

iii. Sulphur dioxide    iv. Hydrogen sulphide.

SET C: Write short note on:

1. Faraday’s laws of electrolysis
2. Le Chatelier’s principle
3. Bohr’s atomic model (postulates)
4. Classical and electronic concept of oxidation and reduction.
5. Law of mass action
6. Hess’s law of constant heat summation.
7. Homologous series
8. Structural isomerism
9. Markovnikov’s rule and anti- Markovnikov’s rule(peroxide effect)
10. Oxidation of alcohols ( identification of primary, secondary and tertiary alcohol )
11. Friedel Crafts reaction.
12. Reduction of nitrobenzene in different media.
13. Diazotization and coupling reaction.
14. Acid rain and Green house effect.
15. Permutit process for the removal of hardness of water.
16. Allotropes of carbon.
17. Different concepts of acids and bases with examples

SET D: Long and 4-marks questions

1. Derive ideal gas equation (PV=nRT)
2. Among CO₂ and SO₂ which one diffuses faster and why?
3. Oxidation and reduction takes place simultaneously ( hand by hand), explain.
4. What is nascent hydrogen? Show that nascent hydrogen is powerful reducing agent than molecular hydrogen.
5. Write significance and limitation of a chemical equation(reaction).
6. Define pH and pOH, Calculate the pH of (i) 0.1 M H₂SO₄ (ii) 0.5 M NaOH solution.
7. What is normality ? How it is related with molarity? How can you prepare N/10 solution of sodium carbonate in 250 ml? (+ other numericals using N₁V₁=N₂V₂)
8. What is solubility? (+ numericals of solubility)
9. What is limiting reagent? (+ numericals of limiting reagent)
10. What are exothermic and endothermic reactions? write examples. Draw energy profile diagram of exothermic and endothermic reaction.
11. What are antipyretics, analgesics, antiseptics, antibiotics and tranquilizers? Write one example of each.

SET E: Very short questions ( 2 marks)

1. What are antacids and antabases , write their (medical) uses.
2. Write down the biological importance of sodium, potassium, magnesium and calcium.
3. Why is CO toxic?
4. Write the Lewis structure of: i. NH₃ ii. H₂SO₄ iii. H₂O , etc
5. Define surface tension and viscosity.
6. How does modern periodic law differs from Mendeleev’s periodic law?
7. Define electrophile and nucleophile with example.
8. What are deliquescent, hygroscopic and efflorescent solids? Write examples too.
9. What are proteins and carbohydrates? List the functions.
10. Identification of aldehyde by Tollen’s reagent( silver mirror test)
11. Identification of alkene(ethene) by Baeyer’s test.
12. Write any two types of chemical reactions with example.
13. State Boyl’s , Charle’s law, Daltons law of partial pressure and Gram’s law of diffusion.
14. Write importance of solubility curve.
15. Differentiate between crystalline and amorphous solid.
16. Define Aufbau principle. Write the electronic configuration of elements having atomic number 20, 24 and 29.
17. Define intermolecular and intramolecular hydrogen bonding with example.
18. Differentiate electrovalent ( ionic) and covalent bond with example.
19. Define oxidant ( oxidizing agent), reductant ( reducing agent) and redox reaction with example.
20. What is ECE (electrochemical equivalent)?
21. Define conjugate acid and bases with example.
22. Show that water acts as both Bronsted- Lowry acid and base.
23. Define one mole and Avogadros number.
24. Define primary and secondary standard solution with examples. Write the requisites for a compound to be primary standard.
25. Differentiate between order and molecularity of reaction.
26. Write short note on wurtz reaction and ozonolysis with example.
27. Chloroform is stored in a dark bottle, why?
28. It is dangerous to boil a sample of ether stored for a long time, why?
29. Differentiate between ortho and para hydrogen.
30. Write name of isotopes of hydrogen with one use of each, what is radioactive isotope?
31. What do you mean by hard and soft water? What are the causes of hardness of water?
32. Write the methods for the purification of drinking water.
33. Define heavy water. Write its one use.
34. Define phosphorescence with reaction.

       See CTEVT chemistry complete notes..

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The complex organic molecules which form the basis of life i.e. which build up living organisms and are also required for their growth and maintenance are called biomolecules. For example : carbohydrates, proteins, nucleic acid, vitamins, etc.

Carbohydrates

Carbohydrates are the polyhydroxy aldehydes, polyhydroxy ketones or large polymeric molecules which on hydrolysis produce polyhydroxy aldehydes or ketones. Eg. glucose, fructose, sucrose, etc.

The carbohydrates which contain aldehyde group are called aldoses while those containing ketonic group are called ketoses.

Classification of carbohydrates :

Carbohydrates can be classified as :

Monosaccharide, Oligosaccharide and Polysaccharide :

Monosaccharides : The simplest carbohydrates which can not be hydrolysed further into any smaller molecules are called monosaccharides. These carbohydrates usually contain 3 to 7 carbon atoms in their molecules. Eg. glucose ( C₆H₁₂O₆), fructose ( C₆H₁₂O₆) , ribose (C₅H₁₀O₅), etc.

Oligosaccharides : The carbohydrates which on hydrolysis give two to nine units of monosaccharides of same type or different types are called oligosaccharides. Oligosaccharides are further classified as di-, tri- and tetrasaccharides.

Disaccharides : Carbohydrates which on hydrolysis produce two molecules of monosaccharides of same or different types are called disaccharides. For example : sucrose, maltose, lactose, etc.

Trisaccharides : Carbohydrates which on hydrolysis produce three molecules of monosaccharides of same or different types are called trisaccharides. For example : raffinose.

Polysaccharides :

These are the polymeric molecules of carbohydrates which on hydrolysis give large number of monosaccharide molecules. For example : starch, cellulose, etc.

The general formula of starch is (C₆H₁₀O₅)_n where n = 100 – 3000.

Sugar and non – sugar :

Sugar : The carbohydrates which are sweet in taste and dissolve in water are called sugars. They are generally crystalline in nature. Eg. glucose, fructose sugar, lactose, etc.

Non – sugar : The carbohydrates which are not sweet in taste and are insoluble in water are called non – sugar. They are generally amorphous in nature. Eg. starch, cellulose, etc.

Note : All monosaccharides and disaccharides are sugar and polysaccharides are generally non-sugar.

Degree of sweetness of sugars :

Fructose > Sucrose > Glucose > Galactose > Maltose > Lactose

Besides carbohydrates some other compounds are far more sweet . eg. saccharine is about 500 times sweet than sucrose. Aspartame, a peptide is about 160 times sweet than sucrose. Monalleine, a protein is about 2000 times sweeter than sucrose.

Reducing and non – reducing sugar

Reducing sugar : Carbohydrates which have ability to reduce Fehling’s solution and Tollen’s reagent are called reducing sugar. Eg. glucose.

Non- reducing sugar : Carbohydrates which do not reduce Fehling’s solution and Tollen’s reagent are called non-reducing sugar. Eg. fructose.

Note : Carbohydrates having aldehyde functional group can reduce Fehling’s solution and Tollen’s reagent.

Q) What are disaccharides ? What happens when they get hydrolysed ?

When disaccharide is hydrolysed then monosaccharides are produced. Eg.

Q) How would you obtain glucose from cane sugar? What is meant by invert sugar ?

Glucose is formed by the hydrolysis of cane sugar with an enzyme i.e. invertase.

Invert sugar : A mixture of equal portion of glucose and fructose obtained by inversion (hydrolysis) of sucrose is called invert sugar. It is found naturally in fruits and honey and produced artificially for use in food industries.

Q) How would you obtain ethanol from cane sugar ? Write reaction only.

Structure of glucose and fructose :

• Glucose has 6 carbon atoms and aldehyde functional group therefore it is also called aldohexose.
• Fructose has 6 carbon atoms and ketone functional group therefore it is also called ketohexose.

Functions of carbohydrates :

• It acts as the major source of energy for animals and human beings.
• It stores chemical energy in plants in the form of sugar and starch.
• It acts as energy storage in animals in the form of glycogen.
• Carbohydrates like cellulose support plant structure.
• Carbohydrates form part of the structural framework of DNA and RNA molecules.
• Carbohydrates add flavor and sweetness to diet.

Protein

The complex nitrogenous organic compounds which are essential for the growth and maintenance of life are called proteins. Proteins are macromolecules in which large number of α – amino acid molecules are linked together by peptide bond ( -CONH- ). Thus proteins are polymers of α – amino acids.

Functions of protein :

Proteins are building blocks of the various tissues. Proteins perform many biological functions such as :

• Catalyze a large number of biological reactions in the form of enzymes. Eg. invertase, maltase, etc.
• Acts as chemical regulators in the form of hormones . Eg. insulin, glucogon, etc.
• Provides natural defense to the body against the entry of antigens into the body system in the form of antibody protein.
• Acts as food reserve in the form of food reserve protein. Eg. egg white .
• Acts as the major structural material of animal tissues in the form of structural protein. Eg. collagen in tendon; keratin in skin, hair, silk, nails and feathers.

Amino acids :

Carboxylic acids containing amino (-NH₂) group attached to any carbon atom other than the carboxylic carbon are called amino acids. Their general formula is:

The naturally found amino acids contain amino group (-NH₂) attached to only α – carbon atom.

Essential and Non – essential amino acids :

• 20 amino acids are required for our body. Human body can synthesize 11 amino acids and 9 must be supplied through diet.
• The amino acids which can be synthesized by our body ( i.e. not necessary in diet) are known as non – essential amino acids. Eg. Glycine, Alanine, ect.
• The amino acids which are not able to synthesize by the body and must be supplied to our body through our diet are known as essential amino acids. Eg. Valine, Phenylalanine, etc.

Zwitter ions :

Amino acids contain both acidic carboxylic (-COOH) group and basic amino (-NH₂) group in the same molecule. In aqueous solution, the –COOH group donates its proton to –NH₂ group of same amino acid forming a dipolar ion. Such dipolar ion of an amino acid is called zwitter ion.

Q) Why are amino acids amphoteric ?

Amino acids contain both acidic carboxylic acid functional group and basic amino group. Due to the presence of both acidic and basic functional group in the same molecule, amino acid is amphoteric in nature.

Peptide linkage ( bond) :

Compound formed by the condensation of two or more same or different amino acids is known as peptide.

During the formation of peptide, – COOH group of one α – amino acid gets condensed with –NH₂ group of other molecule of same or different α – amino acids with the elimination of H₂O molecule. The resulting –CONH₂– linkage is called peptide linkage or peptide bond.

• A peptide formed by the condensation of two molecules of the same or different α – amino acids is called dipeptide.

Q) Explain how amino acids are combined to form a protein molecule.

Proteins are formed by the combination of a number of α – amino acids with the peptide linkage. The -NH₂ group of one α – amino acid condenses with the –COOH group of another molecule of same or different amino acid with the liberation of H₂O molecule.

Hydrolysis of protein :

Proteins on hydrolysis give different types of α – amino acids.

Denaturation of protein :

The process that brings about changes in physical as well as biological properties of the protein without effecting its chemical composition is called denaturation of protein. It is caused by following factors :

• Change in pH
• Change in temperature
• Presence of chemicals (acids, alkalies)

Examples :

• Coagulation of albumin present in white of egg upon heating.
• Coagulation of milk in the presence of lemon juice (acid) to make cheese.

Enzymes :

• Enzymes are biological catalyst produced by living cells which catalyze many biochemical reactions in living systems (i.e. animals and plants).
• Enzymes are also used in huge amount in industrial processes besides the biological reactions. For example: invertase, maltase and amylase enzymes which are present in the yeast are used in breweries and food processing industries.

Note : Some enzymes are associated with some non – protein components called prosthetic group. If the prosthetic group is metal ion it is called a ‘co-factor’ . When the prosthetic group is a small organic molecule it is called a ‘coenzyme’.

Co- enzyme : The non – protein substance associated with enzyme which enhances the catalytic activity of enzyme is called co – enzyme.

Nucleic acid

Nucleic acids are long thread like water soluble macromolecules present in high concentration in the nuclei of all living cells. They are responsible for the transmission of hereditary characters from parents to their off springs and for the biosynthesis of protein.

Nucleic acid are of two types :

• DNA (Deoxyribonucleic acid)
• RNA (Ribonucleic acid)

Basic components of nucleic acid :

• Pentose sugar : ribose gugar and deoxyribose sugar.
• Nitrogenous bases :

Purines – Adenine(A) and Guanine(G)

Pyrimidines – Cytosine(C), Thymine(T) and Uracil(U)

• Phosphate group

Differences between RNA and DNA :

Q) What is the role of hydrogen bonding in the structure of DNA ?

The role of hydrogen bond between two strands (helix) of DNA is to bind them together. Adanine(A) pairs with thymine(T) through two hydrogen bonds and cytosine(C) pairs with guanine(G) through three hydrogen bonds.

Lipids

Waxy or oily substances which are present in all living organism as a main constituent of all cell membrane are called lipids. Actually lipids are the esters of long chain fatty acids and alcohols. Eg. triglyceride of fatty acid.

Note : Fatty acid : Long chain monocarboxylic acids mainly obtained by the hydrolysis of animal fats or vegetable oil. Eg. Palmitic acid (C₁₆) i.e. CH₃(CH₂)₁₄COOH obtained by hydrolysis of palm oil.

Most natural fats and oils are made of one or more mixed glycerides.

Conversion of oils into fats : Hydrogenation or hardening of oil

When oil is hydrogenated unsaturated triglycerides are converted to saturated triglycerides i.e. oil changes to vegetable ghee (vanaspati ghee).

Saponification :

Q) What is soap? How is soap obtained from fat?

Q) What happens when fat (lipid) gets hydrolyzed?

When triglycerides (oil or fat) are hydrolyzed in the presence of sodium or potassium hydroxides glycerol and sodium or potassium salts of fatty acids are formed. The sodium or potassium salts of long chain fatty acids are called soap. This process of formation of soap is called saponification.

See how does soap kills Corona virus……

References:

• Sthapit, M.K., Pradhananga, R.R., Foundations of Chemistry, Vol 1 and 2, Fourth edition, Taleju Prakashan, 2005.
• https://www.britannica.com/science/glucose
• https://www.betterhealth.vic.gov.au/health/healthyliving/protein#:~:text=Protein%20is%20an%20important%20part,used%20as%20an%20energy%20source.
• http://amrita.olabs.edu.in/?sub=73&brch=3&sim=119&cnt=1
• https://courses.lumenlearning.com/introchem/chapter/dna-and-rna/#:~:text=The%20two%20main%20types%20of,to%20carry%20out%20cellular%20functions.

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Unit 2.11 – Aromatic compounds

Definition

Benzene and those cyclic compounds that chemically behave as benzene are called aromatic compounds. Eg.

Structure of benzene

Kekule’s structure of benzene :

Kekule, a German scientist proposed the structure of benzene for the first time. According to Kekule, all the 6 carbon atoms of benzene molecule are joint to each other by alternate single and double bond forming a hexagonal ring and a hydrogen atom is bonded to each carbon atom.

Resonance structure of benzene :

The double bonds may be localized in any position and therefore following resonating structures are possible :

According to these structures, there should be three single bonds (bond length 154 pm) and three double bonds (bond length 134 pm) between carbon atoms in the benzene molecule. But actually it has been found by X- ray diffraction studies that all the carbon-carbon bonds in benzene are equivalent and have bond length 139 pm , which is intermediate between C – C (154 pm) and C = C (134 pm). Thus, the actual structure of benzene is different from both ‘A’ and ‘B’ and is a resonance hybrid of these two resonating forms.

Note: pm = picometre,  1pm = 10 ^-12 m

Nomenclature of aromatic compounds

1. Naming of mono-substituted benzene :

Monosubstituted benzenes are usually named by prefixing the name of the substituent before the word ‘ benzene’. Eg.

However, some of the monosubstituted benzenes are known by their special names.

2. Naming of disubstituted benzene :

• 2 and 6 positions are also indicated by prefix ortho (o-)
• 3 and 5 positions are also indicated by prefix meta (m-)
• Position ‘4’ is also indicated by prefix para (p-). Eg.

If two different substituents are present then, ortho, meta and para is followed by the substituent in an alphabetical order. Eg.

If one of the substituent present in the disubstituted benzene gives the special name then disubstituted benzene is named as derivatives of that special molecule. Eg.

Necessary conditions for any compound to show aromaticity

The necessary conditions for any compound to show aromaticity are as follows :

• The compound must be cyclic and planar and allow cyclic overlap of p-orbitals.
• There must be complete delocalization of π – electrons.
• The compounds must contains π – electrons according to Huckel’s rule, i.e. (4n+2) π – electrons, where n = 0, 1, 2, 3, 4, etc.

Huckel’s rule :

Huckel’s rule states that a cyclic, planar and conjugated molecule is aromatic if it contains 4n+2 delocalized π electrons, where n = 0, 1, 2, 3, 4, etc.

Example : Benzene :

Benzene is cyclic and planar and has cyclic overlap of p-orbitals. There are 3 double bonds i.e. 6 delocalized π – electrons, which is consistant with Huckel’s rule.

i.e. 4n+2 = 6

4n= 4

n = 1(which is an integer)

Therefore, benzene is an aromatic compound. It will show aromaticity.

Preparation of benzene

1. From ethyne ( manufacture of benzene) :

When ethyne gas is passed through a red hot iron or copper tube, the three molecules of ethyne (acetylene) polymerize to give benzene.

2. By decarboxylation of sodium salt of benzoic acid ( Laboratory method) :

Benzene can be prepared by heating sodium salt of benzoic acid ( i.e. sodium benzoate) with sodalime. This reaction is called decarboxylation reaction.

3. By reducing phenol with zinc :

When vapours of phenol are passed over heated zinc dust, benzene is produced.

Chemical properties of benzene

Electrophilic substitution reactions of benzene :

The most important/common reaction of benzene is electrophilic substitution reaction. In this reaction, an electrophile attacks the benzene and substitutes one of the hydrogen atoms of benzene ring. Eg.

1. Halogenation : Benzene reacts with bromine in presence of ferric bromide as catalyst to give bromobenzene.

Similarly, chlorine reacts with benzene in presence of ferric chloride or AlCl₃ as catalyst to give chlorobenzene.

2. Nitration : When benzene is heated with conc. HNO₃ in the presence of conc. H₂SO₄ at about 60⁰C gives nitrobenzene.

3. Sulphonation : When benzene is heated with conc. H₂SO₄ , benzene sulphonic acid is formed.

4. Friedel – Craft’s reaction :

• Friedel-Craft’s alkylation : Introduction of an alkyl group ( – R ) in the benzene ring by treating benzene with an alkyl halide (R-Cl or R-Br) in the presence of anhydrous AlCl₃ is known as Friedel – Craft’s alkylation. Eg.

• Friedel-Craft’s acylation : Introduction of an acyl group (i.e. acyl group) ( ) in the benzene ring by treating benzene with an acylating agent like acid chloride (RCOCl) in the presence of anhydrous AlCl₃ is known as Friedel- Craft’s acylation. Eg.

Uses of benzene

1. It is used as a starting material for the preparation of varieties of aromatic compounds which are used for the manufacture of dyes, drugs, perfumes, explosives, etc. Eg. benzene is used for making toluene which is needed for making TNT.

2. It is used as a solvent for the extraction of fat and oil.

3. It is used as a fuel for automobiles in the name of benzol.

4. It is used for dry cleaning of woolen clothes.

5. It is used for making phenol needed for producing Bakelite.

Nitrobenzene

Laboratory Preparation of Nitrobenzene

It is prepared in lab by heating benzene with conc. HNO₃ and conc. H₂SO₄ at 60⁰C.

Procedure : 50 ml of benzene is taken in a round bottomed flask. To this flask, 60 ml conc. HNO₃ and 60 ml conc. H₂SO₄ (i.e. nitrating mixture) is added a little at a time, shaking and cooling after each addition. Then the mixture is heated (refluxed) in water bath at 60⁰C for about one and half hour till the yellow oily layer appears on the surface. The flask is then cooled and the layer of nitrobenzene is separated by using separating funnel.

Purification : It is first washed with dil. Na₂CO₃ to remove the acidic impurities and then with water severaltimes. It is then dried over fused calcium chloride. It is finally distilled at 211⁰C to get pure nitrobenzene.

Chemical Properties of Nitrobenzene

Reduction of nitrobenzene in different medium :

Nitrobenzene gives different products in different medium by using different reducing agent.

1. Reduction of nitrobenzene in acidic medium :

Nitrobenzene on reduction with Zn/HCl or Sn/ HCl gives aniline.

2. Catalytic reduction of nitrobenzene :

Nitrobenzene when reduced by hydrogen in presence of nickel or platinum as a catalyst gives aniline.

3. Reduction of nitrobenzene in neutral medium :

Nitrobenzene on reduction with Zn and aq. NH₄Cl gives phenyl hydroxylamine.

4. Reduction of nitrobenzene with LiAlH₄ :

Lithium aluminium hydride reduces nitrobenzene to azobenzene.

5. Reduction of nitrobenzene in alkaline (basic) medium :

6. Electrolytic reduction of nitrobenzene :

Nitrobenzene when reduced electrolytically, first gives phenyl hydroxylamine which immediately rearranges to give p- aminophenol.

Aromatic amine (Aniline)

Laboratory preparation of aniline

Aniline is prepared in laboratory by reducing nitrobenzene with tin (Sn) and conc. HCl.

10 ml nitrobenzene and 20 gm of granulated tin are placed in the 250 ml round bottom flask fitted with a reflux condenser. 50 ml of conc. HCl is added gradually with constant shaking. After each addition, the round bottom flask is cooled so that temperature may not go above 90⁰C. Then the reaction mixture is heated on a boiling water bath for about one hour until the reaction is completed which is indicated by the smell of nitrobenzene, the disappearance of smell indicates the completion of the reaction. The flask is then cooled and a crystalline solid mass of double salt is separated out.

The crystalline solid mass is then treated with conc. NaOH until the solution is cleared and becomes strongly alkaline. Aniline is separated out and is floated on the surface as a dark brown oil.

The mixture obtained is then subjected to the process of steam distillation until clear distillate is obtained.

Purification : Aniline is extracted by shaking the distillate several times with ether. The ethereal layer is separated each time with the help of separating funnel. Now, the ethereal aniline is placed for the evaporation where ether evaporates out. Aniline thus obtained is finally purified by redistillation at 182-184⁰C.

Chemical properties of aniline

1. Basic nature of aniline :  Aniline is basic in nature. It reacts with acid to give salt. Eg.

2. Halogenation : Aniline reacts with aq. Bromine ( i.e. bromine water) to give white ppt. of 2,4,6-tribromoaniline.

3. Nitration : Aniline reacts with conc. HNO₃ in presence of conc. H₂SO₄ under proper conditions to give o- and p- nitro aniline.

4. Sulphonation : When aniline is heated with conc. H₂SO₄ gives p-amino benzenesulphonic acid.

Phenols

Preparation of phenol

From diazonium salt (Laboratory method) :

Phenol is prepared in the laboratory by warming an aqueous solution of diazonium chloride.

Chemical properties of phenol

1. Action with zinc dust :  When phenol is heated with zinc dust benzene is formed.

2. Action with NaOH : Phenol behaves as weak acid and reacts with NaOH to form salt and water.

3. Action with ammonia : In the presence of anhydrous ZnCl₂, phenol reacts with ammonia at high temperature to give aniline.

4. Action with PCl₅ : Phenol reacts with PCl₅ to give chlorobenzene.

5. Halogenation : Phenol reacts with aq. bromine ( i.e. bromine water) to give 2,4,6-tribromophenol.

⇐ See note of previous chapters

See the note of next chapter ⇒

References

• Sthapit, M.K., Pradhananga, R.R., Foundations of Chemistry, Vol 1 and 2, Fourth edition, Taleju Prakashan, 2005.
• Finar, I. L., Organic Chemistry, Vol. I and Vol. II, Prentice Hall, London, 1995.
• Ghosh, S.K., Advanced General Organic Chemistry, Second Edition, New Central Book Agency Pvt. Ltd., Kolkatta, 2007.
• Morrison, R.T. , Boyd, R.N., Organic Chemistry, Sixth edition, Prentice-Hall of India Pvt. Ltd., 2008.
• https://www.atsdr.cdc.gov/toxfaqs/tfacts140.pdf
• https://chemicalnote.com/nitrobenzene-laboratory-preparation-properties-and-uses/
• https://chemicalnote.com/aromatic-compounds-structure-preparation-properties-and-uses-of-benzene/
• https://emergency.cdc.gov/agent/benzene/basics/facts.asp#:~:text=Benzene%20is%20a%20chemical%20that,float%20on%20top%20of%20water.

The post CTEVT Organic chemistry(VI)- Aromatic compounds. appeared first on Online Chemistry notes.

Compounds containing carbonyl group.

Nomenclature of Aldehydes and Ketones : eg.

General methods of preparation :

 1. By oxidation of alcohols : Alcohols on controlled oxidation give aldehydes and ketones. Primary alcohols give aldehydes while secondary alcohols give ketones. Acidified K₂Cr₂O₇ or KMnO₄ is used as an oxidizing agent. Eg.

 2. By catalytic dehydrogenation of alcohols : When vapour of alcohol is passed over heated copper at 300⁰C, it gets dehydrogenated. Primary alcohols give aldehydes while secondary alcohols give ketones.

 3. By ozonolysis of alkenes : Alkene reacts with ozone to give ozonide. On warming ozonide with Zn in water, it breaks down to give two molecules of carbonyl compounds (aldehyde or ketone).

Chemical properties of aldehydes and ketones :

 1. Addition of sodium bisulphate : Aldehydes and ketones react with sodium bisulphate solution to form bisulphate addition products. Eg.

2. Addition followed by elimination of water ( Addition of ammonia derivatives) : Aldehydes and ketones react with number of ammonia derivatives such as hydroxylamine (NH₂OH), hydrazine (NH₂NH₂), phenylhydrazine (C₆H₅NHNH₂), etc. in weekly acidic medium to form compounds containing C = N group.

 i. Reaction with hydroxylamine : Aldehydes and ketones react with hydroxylamine to form oximes. Eg.

 ii. Reaction with hydrazine : Aldehydes and ketones react with hydrazine to form hydrazone.

 iii. Reaction with phenylhydrazine : Aldehydes and ketones react with phenylhydrazine to form phenylhydrazone.

iv. Reaction with 2,4-dinitrophenylhydrazine(2,4-DNP test) : Aldehydes and ketones react with 2,4-dinitrophenylhydrazine(2,4-DNP) to form yellow, orange or red ppt. of 2,4- dinitrophenylhydrazone.

 3. Reaction with Tollen’s reagent (silver mirror test) :

Tollen’s reagent is an ammonical solution of silver nitrate. It is prepared by adding solution of NH₄OH to AgNO₃ solution till the precipitate once formed (i.e. Ag₂O) gets dissolved.

Aldehydes on heating with Tollen’s reagent reduces the reagent to metallic silver.

This test is known as silver mirror test. Eg.

 4. Reaction of formaldehyde(methanal) with ammonia :

Formaldehyde reacts with ammonia to form hexamethylenetetramine which is commonly known as urotropine. It is used as medicine to treat urinary infections.

6HCHO + 4NH₃ → (CH₂)₆N₄ + 6H₂O

Structure of urotropine:

Chapter – 9 : Carboxylic acid

Examples of carboxylic acids :

General methods of preparation :

 1. By the oxidation of primary alcohols and aldehydes :

 2. From alkyl benzene :

Aromatic carboxylic acids are obtained by the oxidation of alkyl benzene such as toluene. Eg.

Acidity of carboxylic acids :

Due to presence of polar O – H group, carboxylic acids ionize to giveproton and hence behave as acids.

Effect of substituents on acidic strength of carboxylic acids :

 1. Effect of electron donating substituent :

Q) Why is methanoic acid stronger than ethanoic acid?

Positive inductive effect (+I effect) of electron donating(releasing) groups like alkyl groups( CH₃ – , CH₃CH₂ -, etc.) increases the electron density on O – H bond(group). It makes the release of H⁺ ion difficult. Therefore, the acidic nature decreases with the increase in + I effect. Hence, methanoic acid (formic acid) is stronger acid than ethanoic acid (acetic acid).

2. Effect of electron withdrawing substituent :

Q) Why is chloroacetic acid stronger than acetic acid?

Negative inductive effect (- I effect) of electron withdrawing groups like halogens, – NO₂, -CN, etc. decreases the electron density on O – H bond (group). It makes the release of H⁺ ion easier. Therefore, the acidic nature increases with the increase in – I effect. Hence, chloroacetic acid is stronger acid than acetic acid.

Chemical properties of carboxylic acids :

1. Reaction with base and basic salt ( acidic nature) : Eg.

 2. Reaction with ammonia(Formation of amide) : Carboxylic acids react with ammonia to form ammonium salt which on heating give amides. Eg.

 3. Reaction with PCl₅, PCl₃ or SOCl₂ ( formation of acid chloride) : Carboxylic acids react with phosphorus pentachloride(PCl5), phosphorus trichloride (PCl₃) or thionyl chloride (SOCl₂) to form acid chloride. Eg.

 4. Reaction with alcohols ( Formation of ester) :

Carboxylic acids react with alcohols in the presence of conc. H₂SO₄ or dry HCl to form esters. This reaction is called esterification reaction. Eg.

 5. Formation of acid anhydrides (Dehydration) : Carboxylic acids on heating in the presence of dehydrating agent like P₂O₅ form acid anhydrides. Eg.

Chaper- 10 : Ethers (R – O – R ) 

Examples of ether:

Laboratory preparation of diethyl ether :

When an excess of ethyl alcohol is heated with conc. H₂SO₄ at 140⁰C, diethyl ether is obtained.

Procedure : A mixture of ethyl alcohol and conc. H₂SO₄ in the ratio of 1:1 by volume is taken in the distillation flask. The flask is then fitted with a dropping funnel containing alcohol. The flask is heated on a sand bath at 140⁰C. ethanol is added at nearly the same rate that of the distillation so that the ether formed is continuously received in the receiver kept cold in the ice cold water.

Purification : The distillate thus obtained contains ether, ethyl alcohol, water and sulphurous acid. The acid is removed by washing with KOH or NaOH solution. The solution is then stirred with anhydrous CaCl2 to remove alcohol. Finally it is redistilled to obtain almost pure ether.

Chemical properties of ether :

 1. Reaction involving the ethereal oxygen (Addition reaction) : (Formation of peroxide) :

Q) It is dangerous to boil sample of ether stored for a long time, why?

→ Due to presence of lone pair of electrons on the ethereal oxygen, ether when comes in contact with atmospheric oxygen in the presence of sunlight, it reacts with oxygen to form ether peroxide. Ether peroxide is highly unstable and explodes violently on heating causing serious accidents. Therefore, it is dangerous to boil the sample of ether stored for a long time.

 2. Reactions involving the cleavage of C – O bond ( Fission reaction) :

 i. Reactions with halogen acids(HX) : When ethers are heated with conc. halogen acids( specially HI and HBr), the C – O bond is cleaved and gives alcohol and alkyl halide.

 ii. Hydrolysis : Ether on acidic hydrolysis forms alcohol. Eg.

 iii. Reaction with PCl₅ : When ether is heated with PCl₅, the C – O bonds in the ether are cleaved and alkyl chloride is formed. Eg.

⇐ See previous chapters.

See next chapters ⇒

References :

• Ghosh, S.K., Advanced General Organic Chemistry, Second Edition, New Central Book Agency Pvt. Ltd., Kolkatta, 2007.
• Morrison, R.T. , Boyd, R.N., Organic Chemistry, Sixth edition, Prentice-Hall of India Pvt. Ltd., 2008.
• March, j., Advanced Organic Chemistry, Fourth edition, Wiley Eastern Ltd. India, 2005.
• https://pubchem.ncbi.nlm.nih.gov/compound/Ether
• https://en.wikipedia.org/wiki/Carbonyl_group#:~:text=In%20organic%20chemistry%2C%20a%20carbonyl,to%20as%20a%20carbonyl%20compound.
• https://www.britannica.com/science/carboxylic-acid

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Chapter- 6 : Alkyl halides 

Laboratory preparation of chloroform (trichloromethane) (CHCl₃) :

Principle:  Chloroform is prepared in the laboratory by heating ethanol or acetone with aqueous bleaching powder paste. Bleaching powder paste acts as oxidizing, chlorinating and hydrolyzing agent.

From ethanol :

Step I : Oxidation :

Step II : Chlorination :

Step III : Hydrolysis :

From acetone (propanone) :

Step I : Chlorination :

Step II : Hydrolysis :

Procedure : First of all, bleaching powder paste is prepared by mixing 100 gm of bleaching powder with 200 ml of water in one liter round bottomed flask and 25 ml of ethanol or acetone is added to it. The flask is heated gently on a water bath until a mixture of chloroform and water distills over, as shown in figure . The mixture from receiver is transferred into a separating funnel and the lower layer of chloroform is separated.

Purification : The impure chloroform is washed with dilute caustic soda (NaOH) solution and then with water successively in the separating funnel. It is then dried over anhydrous calcium chloride and redistilled between 60 – 65⁰C. In this way, pure and dry chloroform is obtained.

Chemical properties of chloroform :

 1. Reaction with air : In the presence of sunlight, chloroform is oxidized by air to produce highly poisonous gaseous compound called phosgene (carbonyl chloride).

Thus, chloroform is stored in a dark/coloured bottle to prevent the oxidation of chloroform into phosgene.

 2. Reaction with aq. KOH solution : When boiling with aqueous KOH solution, chloroform is hydrolysed to form potassium formate which on acidification gives formic acid.

 3. Reaction with silver powder : Chloroform when heated with silver powder gives acetylene(ethyne).

 4. Reaction with primary amines ( carbylamine reaction) : When chloroform is warmed with a primary amine in the presence of alcoholic KOH, an offensive(unpleasant) smell of carbylamines ( i.e. isocyanide) is obtained. This reaction is known as carbylamine reaction.

 5. Reaction with phenol (Riemer- Tiemann reaction) : When chloroform is heated with phenol and sodium hydroxide followed by hydrolysis, o – hydroxy benzaldehyde ( salicylaldehyde) is formed. This reaction is called Riemer – Tiemann reaction.

 6. Reaction with acetone(propanone) : Chloroform reacts with acetone in presence of a base such as KOH to give chloretone.

Chloretone is used as a sleep – inducing (hypnotic) drug.

 7. Reaction with HNO₃ : On heating with conc. HNO₃, chloroform gives chloropicrin.

Chloropicrin is used as an insecticide and tear gas.

Uses of chloroform :

1. It is used as an anesthetic. It is now being replaced by other safe anesthetics because chloroform in some cases causes cardiac and respiratory failure.
2. It is used as a laboratory reagent for testing primary amines.
3. It is used for the preparation of chloropicrin, chloretone, salicylaldehyde, etc.
4. It is used in medicines such as a cough syrups.
5. It is used as preservative for biological specimens.

Chapter- 7 : Alcohol

Classification of alcohols :

 1. Monohydric alcohol : Alcohols which contain only one – OH group are called monohydric alcohols.

   Eg. CH₃ – CH₂ – OH (ethanol)

 2. Polyhydric alcohol : Alcohols which contain more than one – OH groups are called polyhydric alcohols. Eg.

• Dihydric alcohol : Alcohol which contains two – OH groups is called dihydric alcohol. Eg.

• Trihydric alcohol : Alcohol which contains three – OH groups is called trihydric alcohol. Eg.

Monohydric alcohols are further classified as primary, secondary and tertiary alcohols according to the nature of – OH bonded carbon atom.

 i. Primary alcohol (1⁰ alcohol) : Alcohols in which – OH bonded carbon atom is further bonded with one or none other carbon atom are called primary alcohols. Eg.

  CH₃ – CH₂ – OH (ethanol)

  CH₃ – OH (methanol)

 ii. Secondary alcohol (2⁰ alcohol) : Alcohols in which – OH bonded carbon atom is further bonded with two other carbon atoms are called secondary alcohols.

 3. Tertiary alcohol (3⁰ alcohol) : Alcohols in which – OH bonded carbon atom is further bonded with three other carbon atom are called primary alcohols.

Preparation of alcohols :

 1. By hydrolysis of haloalkanes : Alcohols are produced when haloalkanes( alkyl halides ) are treated with aqueous sodium or potassium hydroxide.

 2. Industrial preparation of ethanol by fermentation of carbohydrates (molasses) :

Fermentation is a biochemical process of degradarion ( slow decomposition/ breaking down) of large organic molecules like sugars and starches into simpler compounds by the catalytic action of enzymes.

Molasses is the dark coloured liquid left after crystallization of sugar from sugar cane juice. The reactions occurring during the fermentation of sugar(molasses) are :

Chemical properties of ethanol 

 1. Action with sodium metal (acidic nature) :

Ethanol reacts with sodium metal to form sodium ethoxide with the evolution of hydrogen gas.

 2. Action with phosphorus halides (halogenation):

Ethanol reacts with phosphorus halide to form haloethane. Eg.

 3. Action with conc. H₂SO₄ :

When ethanol is heated with conc. H₂SO₄, it undergoes dehydration to give either ether or ethene.

 4. Action with carboxylic acid (esterification reaction) :

Alcohol reacts with carboxylic acid in presence of conc. H₂SO₄ to give ester.

 5. Oxidation of alcohols :

Identification of primary, secondary and tertiary alcohol by oxidation method :

Alcohols are oxidized by different oxidizing agents like acidic or alkaline KMnO₄, acidified K₂Cr₂O₇, dil. HNO₃, etc. to give different products.

 i) Primary alcohols are easily oxidized first to aldehyde and then to carboxylic acids containing same number of C- atoms as in parent alcohol. Eg.

 ii) Secondary alcohols on oxidation give ketones with same number of carbon atoms. The ketones are further oxidized only under drastic conditions ( i.e. prolong treatment of oxidizing agent) to give carboxylic acid containing lesser number of carbon atoms. eg. 

 iii) Tertiary alcohols do not contain hydrogen atom on the carbon carrying – OH group (i.e. α- hydrogen). Thus in order to oxidize tertiary alcohol, a carbon-carbon bond must be broken. For this reason 3⁰ alcohol do not undergo oxidation reaction in neutral or alkaline medium.

But if the oxidation is carried out in the acidic medium under drastic condition tertiary alcohol oxidize to give a mixture of ketone and carboxylic acid. The ketone thus formed further gets oxidized to carboxylic acid. eg.

⇐ See previous chapters

       See next chapters ⇒

References :

• Bahl, B.S., A., Advanced Organic Chemistry, S. Chand and company Ltd, New Delhi, 1992.
• Finar, I. L., Organic Chemistry, Vol. I and Vol. II, Prentice Hall, London, 1995.
• Ghosh, S.K., Advanced General Organic Chemistry, Second Edition, New Central Book Agency Pvt. Ltd., Kolkatta, 2007.
• https://en.wikipedia.org/wiki/Chloroform
• https://brainly.in/question/5234980

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Chapter- 5 : HYDROCARBONS

Alkanes :

Preparation of alkanes by Wurtz Reaction :

When an alkyl halide( haloalkane) is heated with sodium metal in presence of dr ether, an alkane containing double number of carbon atoms than in haloalkane is formed. This reaction is called wurtz reaction.

Alkene :

Preparation of alkenes by dehydrohalogenation of alkyl halide ( elimination reaction):

When alkyl halide is heated with alcoholic solution of sodium or potassium hydroxide, hydrogen and halogen atom is eliminated from adjacent carbon atoms to give alkene. Eg.

Laboratory preparation of ethene(ethylene) :

Ethene gas is prepared in laboratory by heating ethanol with excess amount of conc. sulphuric acid at about 170⁰C.

This reaction takes place in two steps as:

Procedure :

A mixture of 50 ml ethanol and 100 ml conc. sulphuric acid is taken in a round bottom flask and all the apparatus are fitted as shown in figure. Small amount of aluminium sulphate and sad is added to prevent frothing. The flask is then heated to about 170⁰C. The ethylene gas formrd is passed through NaOH solution which absorbs CO₂ and SO₂ present as impurities.

2NaOH + CO₂  → Na₂CO₃ + H₂O

2NaOH + SO₂  → Na₂SO₃ + H₂O

The pure ethylene gas is then collected in a gas jar by downward displacement of water.

Chemical properties of alkenes  :

 1. Addition of hydrogen (Catalytic hydrogenation): When alkenes are heated with hydrogen gas in presence of metal catalyst like Ni, Pt or Pd, alkanes are formed. This reaction is called catalytic hydrogenation.

 2. Addition of halogens : halogens react with alkene in presence of inert solvent like carbon tetrachloride to give dihaloalkane.

Eg. ethene reacts with Br₂ in presence of CCl₄ to give 1,2-dibromoethane. In this reaction reddish brown colour of bromine is discharged. Hence this is a test reaction of ethene(alkene).

 3. Addition of hydrogen halides ( halogen acids)(HCl, HBr, HI) :

Alkene reacts with halogen acids to give alkyl halide (haloalkane). Eg.

When alkene is unsymmetrical then the addition takes place according to Markovnikov’s rule.

Markovnikov’s rule :

This rule states that when an unsymmetrical reagent is added to an unsymmetrical alkene, the negative part of the reagent goes to that double bonded carbon which has lesser number of hydrogen atoms.

For example: The addition of HBr to propene gives 2- bromopropane instead of 1- bromopropane.

Peroxide effect :

When HBr is added to an unsymmetrical alkene in presence of organic peroxide, bromine goes to the double bonded carbon atom having more number of hydrogen. This phenomenon of anti- Markovnikov’s addition of HBr caused by the presence of peroxide is known as peroxide effect or anti- Markovnikov’s rule.

 4. Ozonolysis : Alkene reacts with ozone to give ozonide. On warming ozonide with Zn in water, it breaks down to give two molecules of carbonyl compounds (aldehyde or ketone). This process of formation of ozonide and it’s decomposition to give carbonyl compounds is called ozonolysis.

 5. Polymerization : The process of making polymers from monomers is known as polymerization. Smaller molecules undergoing polymerization are called monomers. The polymers are high molecular weight large molecules made by the polymerization of monomers.

Alkyne :

Laboratory preparation of ethyne (acetylene) :

Ethyne is prepared in laboratory by the action of water on calcium carbide.

Procedure : Small pieces of calcium carbide are taken in a conical flask and all the apparatus are fitted as shown in figure. When water is dropped through dropping funnel, reaction of calcium carbide and water takes place to give acetylene gas. Acetylene gas thus obtained is passed through aqueous copper sulphate solution acidified with dilute HCl to remove impurities like H₂S, PH₃ and NH₃.

The pure acetylene gas is then collected in the gas jar by downward displacement of water.

Chemical properties of alkynes :

 1. Addition of hydrogen ( Catalytic hydrogenation) : When alkyne is heated with hydrogen in presence of Ni, Pt or Pd catalyst, alkane is formed. Eg.

However, alkyne reacts with hydrogen in presence of palladium catalyst deposited over barium sulphate poisoned by sulphur, alkene is formed. Eg.

 2. Addition of water : Catalytic hydration

Alkynes react with water in presence of mercuric sulphate and sulphuric acid to give vinyl alcohol which rearranges to give aldehyde or ketone.

For example, ethyne gives aldehyde.

Propyne gives ketone.

 3. Reaction with bromine solution :

Alkynes react with bromine in water or CCl₄ to give tetrahalo compound. Here, red colour of bromine is discharged. This is test reaction of alkyne(unsaturated compound).

 4. Polymerization reaction : when alkynes are passed through a red hot iron or copper tube, they polymerize to form aromatic compounds.

Eg. Three molecules of ethyne (acetylene) polymerize to give benzene.

 5. Reaction with sodium(Na) metal : Acetylene reacts with Na metal in Liq. NH₃ to form sodium acetylide.

References :

• Finar, I. L., Organic Chemistry, Vol. I and Vol. II, Prentice Hall, London, 1995.
• Ghosh, S.K., Advanced General Organic Chemistry, Second Edition, New Central Book Agency Pvt. Ltd., Kolkatta, 2007.
• https://en.wikipedia.org/wiki/Acetylene
• https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Map%3A_Organic_Chemistry_(Smith)/Chapter_01%3A_Structure_and_Bonding/1.9%3A_Ethane%2C_Ethylene%2C_and_Acetylene

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Chapter – 3 : Isomerism :

Isomers and isomerism in organic compounds :

Different compounds having same molecular formula but different properties are called isomers. The phenomenon of existence of such compounds is called isomerism.Eg.

CH₃ – CH₂ – OH                   CH₃ – O – CH₃

Ethanol                                 methoxymethane

(liquid  at room temp.)       ( gas at room temp.)

Isomerism can be divided into two broad classes :

1. Structural isomerism.
2. Stereoisomerism.

 Structural isomerism : Compounds having same molecular formula but different structural formula are called structural isomers. Phenomenon of existence of such compounds is called structural isomerism.

Structural isomerism can be categorized into following types:

• Chain isomerism
• Position isomerism
• Functional isomerism
• Metamerism
• Tautomerism

• Chain isomerism : Compounds having same molecular formula and same functional group but different in their carbon chain are called chain isomers. The phenomenon of existence of such compounds is called chain isomerism. Examples:

• Position isomerism : The isomers having same carbon chains but different positions of functional group, substituent or multiple bonds( i.e. double or triple bond) are called position isomers . Examples :

• Functional isomerism : Compounds having same molecular formula but different functional groups are called functional isomers. Phenomenon of existence of such compounds is called functional isomerism. Examples :

 Note : Functional isomers:

Alcohol Ether

Aldehyde Ketone

Carboxylic acid Ester

• Metamerism : Compounds having same molecular formula but different in alkyl groups present in the either side of the same functional group are called metamers. The phenomenon is called metamerism. Example:

CH₃ – CH₂ – O – CH₂ – CH₃ (ethoxyethane) and

CH₃ – CH₂ – CH₂ – O – CH₃ (methoxypropane)

Chapter- 4 : Organic reaction :

Inductive effect :

Development of polarity in between the two covalently bonded atoms due to the difference in electronegativity is called inductive effect. This effect is also called field effect or space phenomenon. The inductive effect decreases on increasing the distance

Inductive effect may be represented by arrow in the middle of the bond towards electron withdrawing atom or group.

• Negative inductive effect (-I effect) :

If an atom or group of atoms withdraws electrons, the effect shown by such group is called negative inductive effect (- I effect). Such atoms or groups are more electronegative than carbon atom and also called electron withdrawing species. Some common atoms or groups which cause – I effect are: NO₂, CN, F, Cl, OH, etc.

• Positive inductive effect (+I effect) :

If an atom or group of atoms releases electrons, the effect shown by such group is called positive inductive effect (+ I effect). Such atoms or groups are more electropositive than carbon atom and also called electron releasing species. Some common atoms or groups which cause + I effect are: CH₃ – , CH₃CH₂ – , – O – , etc.

Applications(significance) of Inductive effect:

1. In deciding acidic strength of carboxylic acids.
2. It’s effect on dipole moment and bond length.
3. To decide the stability of carbocation, carboanions and carbon free radicals .

Bond fission( cleavage) :

1. Homolytic bond fission(homolysis) : The cleavage (breaking) of covalent bond in between two atoms in such a way that each atom retains(keeps) one electron of the shared pair of electrons is known as hemolytic fission or homolysis.

Homolytic fission leads to the formation of free radicals. This types of fission takes place when bonding elements have equal or nearly equal electronegativity.

Eg.

2. Heterolytic bond fission(heterolysis) : The cleavage (breaking) of covalent bond in between two atoms in which one of the bonded atoms acquires both of the electrons from shared pair is known as heterolytic fission or heterolysis.

Heterolytic fission leads to the formation of cations and anions. This types of fission takes place when bonding elements have different electronegativity. Eg.

Types of reagents:

1. Electrophiles: Electron deficient atoms or group of atoms which attack on electron rich centre during the reaction are called electrophiles. They are positively charged species or neutral species having electron deficient centre. They are also called electron loving species.

Eg. H⁺, R⁺, AlCl₃, BF₃, etc.

2. Nucleophiles : Electron rich atoms or group of atoms which attack on electron deficient centre during the reaction are called nucleophiles. They are negatively charged species or neutral species having electron rich centre. They are also called nucleus loving species.

Eg. OH ^– , CN ^– , Cl ^– ,:NH₃, H₂O, etc.

• Carbocation: The fragments of organic molecules in which carbon atom bears positive charge are called carbocations. Eg.

CH₃ ⁺ ( methyl carbocation or methylium cation)

CH₃ – CH₂⁺ ( ethylium cation), etc.

• Carbanion: The fragments of organic molecules in which carbon atom bears negative charge are called carbanions. Eg.

CH₃ ^– (methylium anion)

CH₃ – CH₂ ^– ( ethylium anion), etc.

Types of organic reactions :

1. Substitution reactions : A reaction in which an atom or group of atoms is replaced by another atom or group of atoms is called substitution reaction. Types:

i. Nucleophilic substitution reaction

ii. Electrophilic substitution reaction

i. Nucleophilic substitution reaction : A nucleophilic substitution reaction is a chemical reaction which involves the displacement of leaving group by a nucleophile.

It is of two types :

• SN₁ reaction :

→ SN₁ indicates the unimolecular nucleophilic substitution reaction.

→ The rate of SN₁ reaction depends only upon the concentration of the substrate.

i.e. Rate = k[Substrate]

→ The reaction occurs in two steps. In first step carbocation is formed and in second step nucleophile attacks the carbocation to give substituted product. Eg.

• SN₂ reaction :

→ SN₂ indicates the bimolecular nucleophilic substitution reaction.

→ The rate of SN₂ reaction depends upon the concentration of the both substrate and nucleophile.

i.e. Rate = k[Substrate][:Nu ^–]

→ The reaction occurs in single step. . SN₂ reaction occurs through a transition state as shown below: Eg.

ii. Electrophilic substitition reaction :

Electrophilic substitution is a chemical reaction that involves the displacement of a functional group/leaving group by an electrophile.

 2. Elimination reaction:

The reaction in which two atoms or groups of atoms are removed from a molecule and a double or triple bond is formed is called elimination reaction. Eg. dehydrohalogenation reaction of haloalkane.

3. Addition reaction :

Addition reaction is a chemical reaction in which an atom or group of atoms is added to a molecule. Eg.

see next chapters..⇒

References :

• Finar, I. L., Organic Chemistry, Vol. I and Vol. II, Prentice Hall, London, 1995.
• Ghosh, S.K., Advanced General Organic Chemistry, Second Edition, New Central Book Agency Pvt. Ltd., Kolkatta, 2007.
• https://www.chemguide.co.uk/basicorg/isomerism/structural.html
• https://www.sciencedirect.com/topics/chemistry/isomerism
• https://en.wikipedia.org/wiki/Isomer

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CHAPTER- 16 : Chemical Kinetics:

Chemical kinetics is the branch of physical chemistry which deals with the study of reaction mechanism, rate of reaction and the factors affecting the rate of reaction.

Rate of reaction :

Rate of a chemical reaction is the speed or velocity with which the reactants are converted into products.

Let us consider a simple reaction :

Here, rate of reaction = rate of disappearance of A = rate of appearance of B.

Mathematically, Rate = -d[A] / dt = + d[B]/ dt

Hence, “The change in the concentration of reactant or product with change in time is called rate of reaction ”.

Its unit is molL^-1S^-1.

Factors affecting the rate of reaction :

 1. Temperature :

The rate of reaction increases with increase in temperature. It has been found that the rate of reaction nearly doubles for every 10^oC rise in temperature.

 2. Surface area of reactant :

When the surface area of reactant is increased then the rate of reaction increases. For example: powder lime stone reacts more vigorously with dil.HCl than pieces of lime stone.

 3. Concentration of reactant :

When the concentration of reactant increases then rate of reaction also increases. For examples :- Lime stone reacts more vigorously with con. HCl than with dil. HCl.

 4. Catalyst

A catalyst itself doesn’t take part in reaction but affect the rate of reaction. By use of positive catalyst, the rate of reaction increases at particular temperature. Catalyst finds out the alternative new path for the reaction having lower activation energy. A negative catalyst decreases the rate of reaction.

Activation Energy (E_a)

The minimum amount of energy required by the reactant to change into product is called activation energy.

OR, The minimum amount of energy which must be supplied to the reactants to enable them to cross over the energy barrier is called activation energy.

If the activation energy high in a reaction then slower will be the rate of reaction.

Catalyst/ Catalysis :

A catalyst is a substance which provides a new path for the reaction with lower activation energy and speeds up the rate of the reaction.

Enzyme catalysis : Enzymes are also called biological catalysts. Enzymes are protein molecules which act as catalysts to speed up biochemical reactions. Eg.

Order of reaction:

The sum of the powers of concentration in the rate law equation is called order of a reaction.

Let us consider a general chemical reaction,

A + B → Products

We know,

Rate(R) =k [A]^a [B]^b

Where a and b are the order of reaction with respect to A and B respectively.

Therefore overall order of reaction = a+b

If a+b = o then the reaction is zero order reaction.

If a+b = 1 then the reaction is first order reaction.

If a+b = 2 then the reaction is second order reaction and

If a+b = 3 then the reaction is third order reaction.

Rate law equation :

Consider a general reaction

A + B → C

Rate of reaction (R) α [A] [B]

R = K [A] [B] ………(i) where K is rate constant.

This equation (i) is called rate law equation.

If [A] = [B] = 1.

Then R = K

So rate constant (K) can be defined as the rate of reaction when the initial concentration of reactant is unit.

Molecularity of reaction

The total number of atoms, ions or molecules which take part in a chemical reaction is called molecularity of a reaction.

Consider a reaction,

2HI → H₂ + I₂

In this reaction, 2 molecules of reactants are involved in the reaction, so the molecularity of this reaction is 2.

If the molecularity of reaction is 1, the reaction is unimolecular. If the molecularity is 2, the reaction is bimolecular and so on.

Differences between order and molecularity of reaction:

Le-Chatelier’s principle :

If a system in equilibrium is subjected to change in concentration, pressure or temperature then the equilibrium shifts in such a way so as to nullify the effect of the change.

Consider an exothermic reaction,

Total volume of reactant = 4

Total volume of product = 2

Effect of temperature :

It is exothermic reaction. Now, if the temperature is increased i.e. heat is supplied to the system, then according to Le-Chatelier’s principle equilibrium shift to the side that absorbs heat i.e. equilibrium shift in backward direction. Similarly decrease in temperature will shift the equilibrium in the forward direction.

Effect of pressure:

The volume of reactant is more than that of product. When the pressure is increased , the equilibrium shifts to the direction where volume is decreased. So, if the pressure is increased then equilibrium shifts to forward direction. But if pressure is decreased then equilibrium shifts to backward direction.

Effect of concentration :

According to Le-Chatelier’s principle, an increase in concentration of reactants (N₂ and H₂) would shift the equilibrium in that direction in which the reactants are consumed i.e. equilibrium shift in the forward direction. If concentration of NH₃ is increased, the reaction shifts to the backward direction.

Law of mass action :

This principle states that, “the rate of reaction is directly proportional to the product of active masses (i.e. molar concentration) of the reactants.”

Let us consider a general chemical reaction,

At equilibrium, suppose the active masses of A, B, C and D are represented as [A], [B], [C] and [D] respectively. Now, applying the Law of mass action,

Rate of forward reaction (R_f) α [A] [B]

R_f = K_f [A] [B]

Rate of backward reaction (R_b) α [C] [D]

R_b = K_b [C] [D]

At equilibrium,

Rate of forward reaction (R_f) = Rate of backward reaction (R_b)

K_f [A] [B] = K_b [C] [D]

Where K_f is equilibrium constant for forward reaction and K_b is equilibrium constant for backward reaction.

K_f/ K_b =[C] [D] / [A] [B]

K = [C] [D] / [A] [B]

At constant temperature, as K_f and K_b are constant , then K is also constant and is called ‘Equilibrium constant’.

CHAPTER–17: Thermochemistry / Thermodynamics

( thermo=heat)

All the chemical reactions proceed with absorption or evolution of energy. The chemistry dealing with the chemical process and the energy absorbed or evolved during this process is called thermo – chemistry or simply called as chemical thermodynamic.

For example: – In the combustion of fuels like kerosene, coal, wood, etc. energy is evolved whereas in the dissolution of Ammonium chloride in water, heat is absorbed.

The various unit of energy are Joule, Ergs, Calorie, etc.

{1 Joule = 10⁷ ergs , 1 Cal = 4.2 Joule}

Some Thermo – Chemical terms :

 1. System :

A system is the specific portion of universe in which the energy change is to be studied. Water taken in a beaker is an example of a system.

 2. Surrounding :

The remaining portion of universe which is not the part of system is called surrounding. System interacts with the surrounding.

 3. Boundary :

The part that separates system from the surrounding is called boundary. Boundary is that portion of universe through which system and surrounding can interact with each other. Boundary may be real or imaginary.

Internal Energy (E) :

The total amount of energy stored in a system (substance) is called internal energy.

Enthalpy (H) :

Enthalpy is the total heat content of the of a system. It is equivalent to the sum of the internal energy and the product of the pressure and volume of the system.

H = E + PV

Where,

H = Enthalpy, E = Internal Energy, P = Pressure and V = Volume of the system.

Exothermic reaction :

The reaction in which heat is liberated /released from the system is called exothermic reaction.

For example:- In the reaction between a metal and dil. mineral acid, heat is liberated.

Zn (s) + 2HCl (aq.) → ZnCl₂ (aq.) + H₂ (g) + Heat

Endothermic reaction :

The reaction in which heat is absorbed from the surrounding is called endothermic reaction. For example:- In the dissolution of ammonium chloride in water, heat is absorbed from the surrounding.

NH₄Cl (s) + H₂O(l)  →  NH₄Cl (aq.) – Heat

First law of thermodynamics (Law of Conservation of Energy) :

This law state that, “the total energy of the universe i.e. system and surrounding always remains constant, however it may changes from one form to another.” i.e. Energy can neither be created nor destroyed.

Let us consider a system having initial internal energy (E₁). If heat (q) is supplied to the system and work (w) is done on the system then the internal energy in the final stage i.e. E₂ is given as,

E₂ = E₁ + q + w

E₂-E₁ = q + w

Therefore, ∆E = q + w ………..(i)

This equation (i) is the mathematical statement of first law of thermodynamics which shows the relationship among internal energy, work and heat.

Hess’s law (of constant heat summation) :

“The total amount of heat evolved or absorbed in a reaction (i.e. enthalpy change) in a reaction is always same whether the reaction takes place in one step or in a number of steps. In other words, the total amount of heat change in a reaction depends only upon the nature of the initial reactants and the final products and is independent of the path or the manner by which this change is brought about.”

Consider a general reaction

Suppose the heat evolved in this reaction is Q₁ Joules.

Now suppose the same reaction takes place in three steps as follows:

Suppose the heat evolved in these three steps are q₁, q₂ and q₃ Joules respectively.

Thus the total heat evolved (suppose Q₂) = q₁ + q₂ + q₃ Joules.

Then, according to Hess’s law, we must have Q₁ = Q₂

See complete CTEVT note…..

REFERENCES :

• Negi, A.S., Anand, S.C., A Text Book of Physical Chemistry, Seventh Edition, New Age International Pvt. Ltd. Publishers, 1999.
• Atkins, Peter, Paula, de Julio, Atkin’s Physical Chemistry, Seventh Edition, Oxford University Press, (Printed in India, 2002).
• Gurtu, J.N., Snehi, H., Advanced Physical Chemistry, Seventh Edition, Pragati Prakashan India, 2000.
• Madan, R.L., tuli, G.D., Physical Chemistry, S. Chand and company, New Delhi, 2012.
• https://en.wikipedia.org/wiki/Chemical_kinetics
• https://www.ansys.com/blog/chemical-kinetics-basics
• http://www.shodor.org/unchem/advanced/thermo/index.html

The post CTEVT Chemistry note: Physical Chemistry(VII)- Chemical Kinetics and Thermodynamics. appeared first on Online Chemistry notes.

Chapter 10 : ELECTROCHEMISTRY

The branch of physical chemistry which study about the relation between electricity and chemical process involved is called electrochemistry.

Electrolytes:

Electrolytes are the aqueous solution of chemical substance like acid, base and salt which conduct electricity in aqueous medium.

For examples:- Aqueous solution of H₂SO₄, NaOH, NaCl, etc.

Electrolytes are ionized into charge particles (ie. Cation and anion) when electricity is passed through them.

Depending upon the strength of electrolytes, they can be classified into two types.

1. Strong electrolytes
2. Weak electrolytes

Strong electrolytes:-

The electrolytes which are completely ionized in aqueous medium are called strong electrolytes. It can conduct electricity easily.

Examples- Solution of H₂SO₄, HNO₃, HCl, NaOH, NaCl,etc.

Weak electrolytes:-

The electrolytes which are partially ionized in aqueous medium are called weak electrolytes. It conducts electricity partially.

Examples- Solution of CH₃COOH, NH₄OH, H₂CO₃, etc.

Non – Electrolytes :

Non – electrolytes are the aqueous solution of chemical substance which do not conduct electricity in aqueous medium.

Examples – Solution of glucose, sugar, urea etc.

Electrolysis :

The process of chemical decomposition of an electrolytes in solution by using electric current is called electrolysis.

This process is carried out in a vessel called electrolytic cell or voltameter. The two metallic rods are connected to two terminals of battery in electrolytic solution with the help of electric wire. These metallic rods are called electrodes. The electrode connected to positive terminal of battery is called anode and the electrode connected to negative terminal of battery is called cathode. In cathode reduction takes place whereas in anode oxidation takes place.

If the electrolyte is NaCl solution, then,

At cathode : Reduction

At anode : Oxidation

Faraday’s Laws of Electrolysis :

Faraday’s first laws of electrolysis :

This law state that, “The mass of the substance deposited at the electrode during electrolysis is directly proportional to the quantity of electricity passed through the solution.”

Mathematically, w α Q

But, we know, Q=It, then,

w α It

Or, w= ZIt

Where, w = mass(weight) of the substance deposited at the electrode in gram.

Q = quantity of electricity passed through the solution in coulomb.

I= current in ampere

t= time in second

Z= constant known as electrochemical equivalent (ECE).

If I = 1 ampere and t = 1 sec then,

Hence, electrochemical equivalent is the mass of the substance deposited at the electrode by passing 1 Ampere current for 1 second.

{ Note : Z = E/F also. Where F = 1 Faraday’s charge i.e. 96500 coulombs charge and E = Equivalent weight of substances.

i.e. Z= E/96500

1 Faraday’s charge : Charge of one mole of electrons.

We know, charge of an electron = 1.602x10-19

1 mole of electron = 6.023x1023 electrons

Therefore, charge of 1 mole electrons = 6.023x1023x1.602x10-19

= 9.6488x104 = 96488  = 96500 coulombs

i.e. 1 faraday’s charge = 96500 coulombs }

Faraday’s Second laws of electrolysis :

This law states that ” the mass(weight) of different substances deposited or liberated at electrode by the same amount of electricity is directly proportional to the equivalent weight of substances”.

Mathematically, W α E

Or, W = K E

Or, W/E = K

Therefore, Weight of substance (W) / Eq. wt. of substance (E) = Constant (K)

For example, when the same current is passed through the solution of H₂SO₄, CuSO₄ and AgNO₃ for the same period of time as shown in figure, then,

Wt. of the H₂ liberated/ Equivalent weight of H₂ = Constant(K) – – – -(i)

Wt. of the Cu deposited / Equivalent weight of Cu = Constant(K) – – – (ii)

Wt. of the Ag deposited / Equivalent weight of Ag = Constant(K) – – – -(iii)

On combining (i), (ii) and (iii),

It is found that when 1.008 gram of H₂ is evolved from acidified water, then the masses of copper and silver deposited are 31.75 gram and 108 gram respectively, which are the equivalent weight of copper and silver respectively. Hence, this verifies Faraday’s second law of electrolysis.

Applications of Electrolysis :

1. Electrolysis can be used to extract the pure metals in electroplating, electro refining, etc.
2. It can be used to manufacture oxygen and hydrogen gas from water.

Postulates of Arrhenius theory of ionization :

The main postulates of Arrhenius theory of ionization are given below.

• When an electrolyte is dissolved in water or any polar solvent, it’s molecules are dissociated into charged particles called ions. The process of breaking down of molecules into ions is called ionization.
• Positively charged ions are called cations and negatively charged ions are called anion.
• Number of cations and anions in the solutions is always equal. So, the solution becomes electrically neutral.

• Ions have tendency to reunite to form unionized molecules too. So an equilibrium exists between the ions and unionized molecules.

• The degree of ionization vary with concentration . Lower the concentration of dissolved substance, greater is the degree of ionization.

Thus complete ionization(dissociation) may be expected to take place only in infinitely dilute solutions.

• The properties of an electrolyte in solution are the properties of it’s ions.

pH : pH may be defined as negative logarithm of hydrogen ion concentration.

i.e. pH = -log [H⁺]

Auto – ionization of water/ Relation between pH and pOH :

Water is a weak electrolyte which ionizes weakly as,

Applying law of mass action,

Or, k[H₂O] = [H⁺] [OH^–]

Or, k_w = [H⁺] [OH^–]

Where K_w is a constant called ionic product of water and is defined as the product of molar concentration of H⁺ and OH^– ions at temperature of 25⁰C. it’s value at 25⁰C is found to be 1×10^-14

Therefore, [ H⁺ ] [ OH^– ] = 1×10^-14

Taking –log on both sides,

-log [ H⁺ ] – log [ OH^– ] = -log [ 1×10^-14 ]

p^H + p^OH = 14 …………………. ( i )

This equation ( i ) is the relation between p^H and p^OH.

p^H Scale :

The scale or the instrument which is used to measure the p^H of the solution is called p^H scale.

If a solution have:

p^H = 7 ( Then solution is neutral. )

p^H< 7 ( Then solution is acidic.)

p^H> 7 ( Then solution is alkaline.)

Importance of p^H

1. p^Hplays important role in the digestion of food and other biochemical activities. Examples : p^H of gastric juice is 1 – 2 which help in digestion of food.
2. Enzymes function effectively at certain p^H. Example : Trypsin acts best in alkaline p^H.
3. p^H of blood is maintained at the p^H of 7.35 – 7.42 which is due to the buffer action of bicarbonate and carbonic acid system.

Buffer solution :

The solution which can resist the p^H of the solution when small amount of acid or base is mixed in it is called buffer solution.

OR, The solution of equimolar mixture of a weak acid and its salt with strong base or weak base and its salt with strong acid is called buffer solution.

There are two types of buffer solution.

• Acidic Buffer : It is the solution of equimolar mixture of a weak acid and its salt with strong base. Eg. Equimolar mixture of CH₃COOH and CH₃COONa . The pH value of acidic buffer is less than 7.

• Basic(alkaline) Buffer: It is the solution of equimolar mixture of a weak base and its salt with strong acid. Eg. Equimolar mixture of NH₄OH and NH₄Cl. The pH value of acidic buffer is more than 7.

Applications of buffer solution:

1. Buffer action maintains the p^H of blood at about 7.35 – 7.42. If p^H is slightly changed then it may cause death.
2. It is used in many industrial processes like electroplating, manufacture of dyes, food, etc.
3. It is used in analytical chemistry.
4. It is used in bacteriological research.

Common – ion effect :

When a strong electrolyte having a ion common to weak electrolyte is mixed, then the ionization of weak electrolyte is totally suppressed. This effect of ion is called common ion effect.

This effect is used in soap industries to make the precipitate of soap from soap solution.

Numerical solved problems :

• Find the p^H of 0.1 Molar (M) of HCl.

Solution:-

HCl      →    H⁺ +    Cl^–

0.1M        0.1M     0.1M

We know that,

p^H = -log [ H⁺ ]

= -log [0.1]     = 1 ans.

• Calculate the p^H of 0.5 M solution of sulphuric acid.

Solution:-

H₂SO₄     →   2H⁺   +   SO₄^—

0.5M         2×0.5M      0.5M

We know,

p^H = -log [ H⁺ ] = – log [2×0.5] = 0 ans.

• Calculate the pH of solution containing [OH^–] ions concentration of 10^-6 mol L^-1

Solution:

Given, [OH^–] = 10^-6 mol L^-1

pH = ?

we know pOH = -log[OH^–]

= – log10^-6      = 6

Now , pH + pOH = 14

Therefre, pH = 14 – pOH = 14 – 6 = 8 ans.

• A current of 2.5 Ampere is passed through a solution of ZnSO₄ for 30 minutes and deposits 1.52 gram at cathode. Calculate the equivalent weight of zinc.

Solution:-

Given,  Current (I) = 2.5 A

Time (t) = 30 minutes = 30×60 sec = 1800 seconds

Weight of zinc deposited( w ) = 1.52 gram

Equivalent weight of Zinc ( E ) = ?

We know from first law of electrolysis,

w = ZIt

w = E/96500 x It

1.52 = E/96500 x 2.5 x 1800

E = 32.59

Thus, equivalent weight of zinc is 32.59.

• 0.383 gram of divalent metal was deposited by passing 2 Ampere of current for 50 minutes. Calculate the atomic weight of metal.

Solution:-

Given,

Weight of metal ( w ) = 0.383 gram

Current ( I ) = 2 A

Time ( t ) = 50 minutes = 50×60 sec = 3000 second

Valency of metal ( V ) = 2

Atomic weight of Metal ( At. Wt.) = ?

We know,

m = Zit

m = E/96500 x It

0.383 = E/96500 x 2 x 3000

E = 6.15

Again,

Equivalent weight ( E ) = Atomic weight/Valency

6.15 = At. Wt./2

At.Wt. =12.30

Therefore, atomic weight of zinc is 12.30 gram.

• How many coulombs of electricity is required to discharge 0.1 M of sodium.

Solution:-

We know,

1 mole of Na discharge 1 Faraday’s coulombs charge.

i.e. 1 mole of Na discharges 96500 coulombs.

0.1 M of Na discharge 96500 x 0.1 Coulombs.

= 9650 coulombs

Therefore, 9650 coulombs of electricity is required to discharge 0.1 M of sodium.

CHAPTER 11  : Acids, Bases and Salt:

Different Concepts of Acids and Bases :

1. Arrhenius Concept of Acids and Bases :

• An acid is a compound which gives H⁺ ions in water. Eg.

• A base is a compound which gives OH^– ions in water. Eg.

 2. Btonsted – Lowry Concept of acids and bases :

• An acid is a substance that can donates a proton.
• A base is a substance that accepts a proton. Eg.

Here HCl donates proton and H₂O accepts proton. Hence HCl is an acid and H₂O is base.

 3. Lewis concept of acids and bases:

• An acid is a substance which can accept a pair of electrons.
• A base is a substance which can donate a pair of electrons.

Conjugate Acid- Base pair :

A pair of acid and base that differs from each other by a single proton is known as conjugate acid – base pair.

In this reaction Hydrochloric acid and chloride ion are conjugate acid- base pair. Similarly, hydronium ion and water are another conjugate acid – base pair.

Some examples of Acids and Bases :

Strong acids : HI > H₂SO₄ > HCl > HNO₃ , etc.

Strong bases : NaOH > KOH > Mg(OH)₂ > Ca(OH)₂ , etc.

Weak acids : HCOOH, CH₃COOH, HF, H₂S, H₂CO₃, etc.

Weak bases : NH₃, NH₄OH, etc.

Salt and it’s types :

A salt is an ionic compound that results from the neutralization reaction of an acid and a base.

Eg. NaCl, KCl, Na₂CO₃, CuSO₄ etc.

Arrhenius concept: Those substances which gives cation except H+ and anion except OH- when dissolves in water is Arrhenius salt. Eg. NaCl.

 1. Acidic salt : Salt formed by the reaction between strong acid and weak base is called acidic salt.

 2. Basic salt : Salt formed by the reaction between strong base and weak acid is called acidic salt.

 3. Neutral salt : Salt formed by the reaction between strong acid and strong base is called acidic salt.

Antacids , Antabases and their medical uses :

 1. Antacid : An antacid is a substance which neutralizes acidity of our body i.e. stomach acidity. It generally contains weak bases like magnesium hydroxide, aluminium hydroxide, sodium carbonate, etc.

Medical use : It is used to relieve occasional heartburn, indigestion and gastritis.

2. Antabase : An antabase is a substance which neutralizes basicity of our body. It generally contains weak acids like acetic acid, citric acid, etc.

Medical use : It controls and neutralizes the base present in our body. It is used to relief the pain of wasp bite. It is used to maintain the pH value of urine and prevents kidney diseases.

REFERENCES :

• Atkins, Peter, Paula, de Julio, Atkin’s Physical Chemistry, Seventh Edition, Oxford University Press, (Printed in India, 2002).
• Gurtu, J.N., Snehi, H., Advanced Physical Chemistry, Seventh Edition, Pragati Prakashan India, 2000.
• Madan, R.L., tuli, G.D., Physical Chemistry, S. Chand and company, New Delhi, 2012.
• Negi, A.S., Anand, S.C., A Text Book of Physical Chemistry, Seventh Edition, New Age International Pvt. Ltd. Publishers, 1999.
• https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Electrochemistry
• https://bouman.chem.georgetown.edu/S02/lect25/lect25.htm
• https://courses.lumenlearning.com/boundless-chemistry/chapter/acid-base-properties-of-salts/
• https://www.bbc.co.uk/bitesize/topics/zjmpgwx
  

  ---

See complete note…

The post CTEVT Chemistry : Physical(V)-Electrochemistry and Acids, Bases and Salts. appeared first on Online Chemistry notes.

CHAPTER-8 : METALS

Metals are those natural elements which are generally solid, hard, lustrous and higher in density. Metals have a very high boiling and melting point. They effectively conduct heat and electricity. In metals, the atoms are arranged in the crystal structure.

Metals generally contain 1,2, or 3 electrons in their outermost shell. Some examples of metals are silver, aluminium, gold, lead, nickel, copper, magnesium, iron, cobalt, zinc, etc.

Differences between metals and non-metals :

Differences between minerals and ores

Differences between flux and slag :

Differences between calcinations and roasting :

Chemistry ( Preparation, properties and uses) of some compounds :

 1. Plaster of Paris (CaSO₄. 1/2H₂O) :

Plaster of Paris is calcium sulphate hemihydrate and is represented by CaSO₄. 1/2H₂O or 2CaSO₄. H₂O.

Preparation: It is prepared by heating gypsum (rock) at about 140^oC.

Properties :

1. It is white and amorphous powder.
2. It is insoluble in water.
3. When powdered plaster of Paris is mixed with little water, it is converted into its paste which sets into hard solid mass within 5 to 15 minutes. This process is called setting of plaster.

Uses :

1. It is used in surgery for plastering (i.e. setting) the fractured bones.
2. It is used for making molds (casts) for statues and other decorative materials.
3. Used for making black board chalk.
4. Used for making artificial marble.

 2. Bleaching powder (CaOCl₂) :

Its chemical name is calcium oxychloride or calcium chloro hypochlorite Ca(ClO)Cl.

Preparation : It is prepared by the action of chlorine gas on dry slaked lime.

Properties :

1. It is pale yellow amorphous powder.

2. Solubility : It is soluble in water. It gives Ca(OH)₂ and Cl₂ with water.

3. Action of air : When bleaching powder is exposed to air, it reacts with atmospheric carbon dioxide liberating Cl₂ hence odour of chlorine is produced from bleaching powder.

4. Catalytic decomposition : When bleaching powder is heated with cobalt chloride as catalyst, Oxygen gas is evolved.

5. Bleaching action : When bleaching powder is mixed with small quantity of dilute mineral acid, hypochlorous acid is formed, which decomposes giving nascent oxygen. This nascent oxygen is responsible for converting coloured substance into colourless substance.

Uses :

1. It is used as bleaching agent.
2. It is used in the manufacture of chloroform (CHCl₃).
3. It is used as germicide and disinfectant in the purification of drinking water.

 3. Epsom salt ( MgSO₄. 7H₂O) :

Epsom salt is chemically magnesium sulphate heptahydrate( MgSO₄. 7H₂O).

Preparation :

1. Commercially, it is prepared by the action of dilute sulphuric acid on magnesium carbonate ( magnesite ore).

The resulting aqueous solution is subjected to crystallization to get crystals of Epsom salt.

2. It is also prepared by the action of dilute sulphuric acid on dolomite.

The insoluble CaSO₄ is removed by filtration and filtrate is crystallized to obtain crystals of Epsom salt.

3. Magnesium sulphate is prepared by dissolving magnesium metal or magnesium oxide with dil. H₂SO₄.

The solution is concentrated and on cooling crystals of magnesium sulphate, MgSO₄. 7H₂O are formed.

Properties :

1. It is colourless crystalline solid.

2. It is efflorescent in nature.( loses water of crystallization slowly)

3. Action of water : It is highly soluble in water. The aqueous solution of magnesium sulphate is acidic in nature due to formation of strong acid and weak base.

4. Action of alkali : It gives white precipitate of magnesium hydroxide with caustic alkali solution.

5. Action of heat : when it is heated to about 200⁰C, anhydrous form is obtained. On further heating, it decomposes to give MgO and SO₃ gas.

Uses :

1. It is used as a purgative (laxative) in medicine.
2. It is used to correct magnesium and sulphur deficiency of soil.
3. It is used to prepare fire proof fabrics.
4. It is used in the manufacture of paint, soap, etc.

 4. Silver nitrate:

Preparation : silver nitrate is prepared by dissolving silver metal in warm dil. nitric acid. The resulting solution is crystallized to obtain silver nitrate crystal.

Properties :

1. It is colourless and crystalline solid.

2. It is soluble in water.

3. When it is strongly heated, it decomposes to form metallic silver.

4. Action with halides: AgNO₃ solution reacts with halides to give ppt. of silver halides.

5. Action with ammonia : Silver nitrate reacts with ammonia to form a complex i.e. diamine silver nitrate.

6. Action with sulphide salt: Silver nitrate solution reacts with metal sulphide to form black ppt. of silver sulphide.

Uses :

1. It is used as laboratory reagent to detect halides.
2. It is used to prepare Tollen’s reagent.
3. It is used to prepare silver halide salts used in photography.
4. It is used in preparation of indelible (permanent) ink.

 5 . Calomel(Hg₂Cl₂) :

Calomel is mercurous chloride , Hg₂Cl₂.

Preparation :

1. It can be prepared by heating mercury with mercuric chloride.

2. It can be prepared by treating mercurous nitrate solution with chloride salts.

3. It can be prepared by the action of mercuric chloride with stannous chloride.

Properties :

1. It is white amorphous solid.

2. It is insoluble in water. However, it dissolves in chlorine water forming mercuric chloride.

3. It decomposes on heating to give metallic mercury and mercuric chloride.

4. Calomel is reduced by stannous chloride to give metallic mercury.

5. It reacts with alkali like NaOH to give black ppt. of Hg₂O.

Uses :

1. It is used as purgative in medicine.
2. It s used to make calomel electrode (which is used as standard reference electrode).
3. It is used as fungicide.

 6. Corrosive sublimate ( HgCl₂) :

Corrosive sublimate is mercuric chloride, HgCl₂.

Preparation :

1. It is prepared by heating mercury with excess of chlorine.

2. It is prepared by heating mercuric sulphate with sodium chloride.

3. It can also be prepared by treating mercuric oxide with dilute hydrochloric acid.

Properties :

1. It is white crystalline solid.

2. It is soluble in water and organic solvents such as alcohol, ether, etc.

3. It is highly poisonous and causes death.

4. When it is heated with mercury, it gives mercurous chloride.

5. Mercuric chloride reacts with stannous chloride and formes mercurous chloride.

6. HgCl₂ solution reacts with NaOH to give yellow ppt. of mercuric oxide.

Uses :

1. It is used as a fungicide in agriculture.
2. As antiseptic to sterilize surgical instruments.
3. As a preservative of wood(timber)

 7. Red oxide of copper ( Cu₂O) :

Cuprous oxide or copper(I) oxide is commonly called red oxide of copper.

Preparation :

1. It is prepared by the reduction of cupric oxide using reducing agent like glucose solution.

2. It is prepared by heating copper in air above 1100⁰C.

Properties :

1. It is reddish amorphous powder.

2. It is insoluble in water.

3. When red oxide is heated strongly in air, it turns to black oxide of copper(cupric oxide).

4. It reacts with hydrogen on heating to form metallic copper.

5. It is a basic oxide and reacts with conc. HCl to give cuprous chloride salt.

Uses :

1. It is used in glass industry to prepare red coloured glass.
2. It is used as an antirust paint.

CHAPTER- 9 : Minerals

Minerals are substances that are formed naturally in the Earth. Minerals are usually solid, inorganic, have a crystal structure, and form naturally by geological processes.

Minerals in food : Minerals are inorganic nutrients found in foods that are essential for growth and health and do not contain the element carbon.

Mineral	Function (biological importance)	Sources	Deficiency
Sodium (Na)	Needed for proper fluid balance (regulate osmotic pressure of body fluids), for generation of nerve impulses and muscle contraction.	Table salt(sodium chloride); Large amounts in processed foods, Small amounts in milk, breads, vegetables, and unprocessed meats.	The Improper functioning of nerves and muscles, Nausea, cramps, vomiting, dizziness, possible respiratory failure.
Potassium (K)	Needed for proper fluid balance (regulate osmotic pressure of body fluids), Influences muscle activity, especially cardiac muscle.	Meats, milk, Fruits especially banana, orange juice and dried fruits, Vegetables	Muscle weakness Cardiac diseases Respiratory failure
Calcium (Ca)	Important for healthy bones and teeth; Helps muscles relax and contract; Important in nerve functioning, blood clotting, blood pressure regulation, immune system health.	Milk and milk products; Fish with bones, Green vegetables(broccoli, mustard greens); legumes, “hard” drinking water.	Ricket- abnormal development of bones, osteoporosis : when you’re older, your bones break very easily due to the slow loss of bone mass short-term deficiency may cause muscle cramps, stiffness(inflexibility) and poor mobility.
Magnesium (Mg)	Needed for making proteins. Found in bones; Muscle contraction, nerve impulse transmissions, immune system health.	Milk, Nuts and seeds (legumes); Leafy, green vegetables; Sea food; chocolates. “hard” drinking water	Muscle tremors (shaking), seizure. Irritability (state of being irritate).
Iron (Fe)	Essential for the formation of haemoglobin found in red blood cells that carries oxygen in the body; Increases resistance to infection Functions as part of enzymes involved in tissue respiration Needed for energy metabolism.	Organ meats; red meats; fish; poultry; shellfish (especially clams); Egg yolks; legumes; Dried fruits; Dark, leafy greens; iron-enriched breads and cereals.	Iron deficiency cause anemia: it happens due to decrease in number of haemoglobin in red blood cells. Symptoms can include headache, chest pain, and pale skin. Irritability, lethargy.
Zinc (Zn)	Part(component) of many enzymes; needed for making protein and genetic material; has a function in taste perception, wound healing, .normal fetal development, production of sperm, normal growth and sexual maturation, immune system health.	Meats, fish, poultry, leavened whole grains, vegetables.	Decreased wound healing, decreased taste acuity, hair loss, diarrhea, growth failure (retardation)

⇐  See previous chapters.. . 

REFERENCES :

• Lee, j. D., Concise Inorganic Chemistry, Fifth Edition, Joh, Wiley and Sons, Inc., 2007.
• Sarkar, R., General and Inorganic Chemistry, Second Edition, New Central Book Agency(P) Ltd., India, 2007.
• Shriver, D. F., Atkins, P. W., Inorganic Chemistry, Fifth Edition, Oxford university Press, 2010.
• Agrawal, S. K., Lal, K., Advanced Inorganic Chemistry, Fifth Revised Edition, Pragati Prakashan, Meerut, 2001.
• Cotton, F. A., and Wilkinson, G., Advanced Inorganic Chemistry, Fifth edition, John Wily and Sons, Singapore, 1995.
• Day, C.M., Selbin, J., Theoritical inorganic Chemistry, second edition, Affiliated East-West Press Pvt. Ltd., New Delhi, 2002.
• Mitra, L.A. , A Text Book of Inorganic Chemistry, Ghos and Company, 61^st edition, 1996.
• https://www.thoughtco.com/metals-versus-nonmetals-608809
• http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/metal.html
• https://www.britannica.com/science/silver-nitrate
• https://en.wikipedia.org/wiki/Silver_nitrate
• https://www.sciencedirect.com/science/article/abs/pii/S1002016013600776
• https://www.healthlinkbc.ca/health-topics/ta3912
• https://www.researchgate.net/publication/259520065_Sources_and_Deficiency_Diseases_of_Mineral_Nutrients_in_Human_Health_and_Nutrition_A_Review

The post CTEVT Chemistry Note : Inorganic Chemistry(IV) : Metals and Minerals. appeared first on Online Chemistry notes.