Q27 of 30 Page 1

Describe the following giving one example for each:

i. Detergents


ii. Food preservatives


iii. Antacids


(i) Detergents: They are sodium salts of long chain alkyl sulphonates or benzene sulphonates. In other words, detergents are soluble salts of sodium potassium sulphonic acids. Unlike soaps they are mostly non-biodegradable but they can be conveniently used both with soft and hard water. e.g. Sodium alkylbenzene sulphonate, Sodium Lauryl sulphate, etc.


(ii) Food preservatives: They are the chemicals which are used to preserve food by preventing microbial growth e.g. Sodium benzoate, Table salt, etc.


(iii) Antacids: The substances which are taken to neutralize the excess acid and maintaining the pH to an appropriate level in stomach are called antacidse.g., NaHCO3 and Milk of magnesia.


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25

Answer the following:

(i) Haloalkanes easily dissolves in organic solvents, why?


(ii)What is known as a racemic mixture? Give an example.


(iii)Of the two bromo-derivatives, C6H5CH(CH3)Br and C6H5CH( C6H5)Br, which one is more reactive in SN1 substitution reaction and why?


 26

(a) Explain why an alkylamine is more basic than ammonia?
(b) How would you convert:
(i) Aniline to nitrobenzene
(ii)Aniline to iodobenzene

 28

(a) Differentiate between molality and molarity of a solution. How does a change in temperature influence their values?
(b) Calculate the freezing point of an aqueous solution containing 10.50 g of MgBr2 in 200 g of water. (Molar mass of MgBr2 = 184 g) (Kƒ for water = 1.86 K kgmol-1

OR


(a) Define the terms osmosis and osmotic pressure. Is the osmotic pressure of a solution a colligative property? Explain
(b) Calculate the boiling point of a solution prepared by adding 15.00 g of NaCl to 250.0 g of water. (Kb for water = 0.512 K kg mol-1, Molar mass of NaCl = 58.44 g)


 29

(a) Give chemical tests to distinguish between

(i) Propanal and propanone,


(ii) Benzaldehyde and acetophenone.


(b) How would you obtain


(i) But-2-enal from ethanal,


(ii) Butanoic acid from butanol,


(iii) Benzoic acid from ethylbenzene?


OR


(a) Describe the following giving linked chemical equations:


(i) Cannizzaro reaction


(ii) Decarboxylation


(b) Complete the following chemical equations: