The entropy of vaporization of acetic acid is:

Less than 21 cal deg - 1 mole - 1

greater than 21 Joule deg - 1 mole - 1

equal to 21 Joule deg - 1 mole - 1

greater than 21 cal deg - 1 mole - 1

An organic compound A C 7 H 6 O has the smell of bitter almonds. Compound A reacts with ammonia to give compound B C 21 H 8 N 2 . Compound A also reacts with a dilute alcoholic KCN to form compound C C 14 H 12 O 2 . Identify A , B and C . Explain the reaction.

The chemical formula of Benzaldehyde is C 6 H 5 - CHO , and has the smell of bitter almonds. (I) When Benzaldehyde reacts with ammonia, so Hydro benzamide C 21 H 8 N 2 is formed. 3 C 6 H 5 - CHO A - Benzaldehyde + 2 NH 3 → C 6 H 5 CH C 6 H 5 CH = N 2 B - Hydro benzamide + 3 H 2 O (II) When benzaldehyde is treated with alcoholic potassium cyanide, so benzoin is formed. 2 C 6 H 5 - CHO A - Benzaldehyde → Alc . KCN C 6 H 5 - CH OH - CO - C 6 H 5 C - Benzoin

How is oxalic acid prepared industrially from sodium formate?

Solid sodium hydroxide and carbon monoxide react together at high temperatures and high pressure to produce sodium formate, then the reaction mixture was collected in a precipitator and calcium hydroxide was added to it with constant stirring. By this reaction, the calcium oxalate and sodium hydroxide are formed which are separated by filtration. The filtered calcium oxalate is treated with a small amount of calcium carbonate and then treated with dilute sulphuric acid, so, calcium sulphate dihydrate is formed. This mixture is taken to a crystallizer and crystals of oxalic acid are formed. 2 HCOONa Sodium formate → NaOH COONa 2 Sodium oxolate → H 2 SO 4 Ca OH 2 COOH 2 Oxalic acid

How is oxalic acid prepared by laboratory method?

The oxalic acid is prepared by the reaction of cane sugar with nitric acid in the presence of a small quantity of Vanadium pentoxide in the laboratory. These can be done in the following steps: (i) The sugar is placed in a flask and nitric acid is added to it. Then, it is heated in a boiling water bath, so the fumes of nitric acid are produced. (ii) On producing the fumes of nitric acid, the flask is removed from the water bath and placed on a surface. (iii) After some time, it is removed in evaporating basin and heated two times with some time intervals. Then, it is cooled in an ice-water bath. By this process, the crystals of oxalic acid are formed which are separated out the filtration after washing with hot water. C 12 H 22 O 11 Cane sugar + HNO 3 → V 2 O 5 COOH 2 Oxalic acid

Explain the use of radioactive isotopes in the study of the mechanism of photosynthesis in plants and the hydrolysis of esters.

The elements which have the same atomic number, but differ in the number of neutrons or atomic mass are called isotopes. Radioactive isotopes have an unbalanced combination of proton and neutrons. (I) The use of radioactive isotope in the study of the mechanism of photosynthesis- Photosynthesis is a chemical process that occurs in plants in the presence of sunlight and chlorophyll. In this process, atmospheric carbon dioxide is reacted with cellular water in the presence of sunlight and chlorophyll, so glucose is formed and oxygen is released. By the use of radioactive isotope of oxygen O 18 in ordinary carbon dioxide molecules, it has been proved that the production of oxygen is carried out by the water molecule, not from the carbon dioxide molecule. (II) By the use of radioactive isotope of O 18 , the hydrolysis mechanism of the ester can be understood. In the hydrolysis of ester, the - OH group of the water molecules is retained in acid formation.

Give suitable reaction to show that trans esterification is an alcoholysis reaction.

When an ester is refluxed with an excess of the alcohol in the presence of HCl gas or sodium alkoxide(catalyst), the alkyl group of the ester molecule is replaced by another alkyl group(usually a lower one). This process is known as trans-esterification or alcoholysis of ester by alcohol. The following reaction will show the splitting of ester by alcohol- CH 3 COOC 2 H 5 Ethyl acetate + CH 3 OH Methanol → NaOCH 3 CH 3 COOCH 3 Methyl acetate + C 2 H 5 OH Ethanol

Explain the isomerism exhibited by carboxylic acid.

The carboxylic group is - COOH group. This group can exhibit two types of isomerism: (I) Chain isomerism- The isomerism in which the chemical formula of the compounds are the same, but they differ in the positions of side chains or the number of carbons in the main chain is called chain isomerism. CH 3 - CH 2 - CH 2 - COOH Butanoic acid ⇌ CH 3 - CH 2 - | CH 3 COOH 2 - methyl Propanoic acid (II) Functional isomerism- The isomerism in which the chemical formula of the compounds are the same, but they differ in their arrangement of atoms and functional group. CH 3 - CH 2 - COOH Propanoic acid ⇌ CH 3 - COO - CH 3 Methyl methanoate

Explain the mechanism of the Claisen Schmidt reaction.

Claisen Schmidt reaction- When aldehyde or ketone with alpha hydrogen is treated with benzaldehyde in the presence of sodium hydroxide, so aromatic aldehyde is formed. This reaction is known as the Claisen Schmidt reaction, and it is a cross aldol condensation type of reaction. The mechanism of this reaction is the following: (I) The acetaldehyde gets a negative charge on reacting with sodium hydroxide by losing alpha hydrogen which further reacts with benzaldehyde and forms an aromatic aldehydic compound. (II) On heating this compound, the water molecule gets separated, and the aromatic aldehyde is formed.

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter -1 - Carbonyl Compounds and Carboxylic Acids>Tamilnadu Board-2018>Q 5

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12th Tamil Nadu Board

IMPORTANT

Earn 100

In crossed Cannizzaro reaction between formaldehyde and benzaldehyde the alcohol formed is only benzyl alcohol and not methanol. Give reason.

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