How would you distinguish experimentally between an alcohol and a carboxylic acid on the basis of a chemical property?

28 Give reasons for the following observations:

(a) Air holes of a gas burner have to be adjusted when the vessels being heated get blackened by the flame.

(b) Use of synthetic detergents causes pollution of water.

29 What would be observed on adding a 5% alkaline potassium permanganate solution drop by drop to some warm ethanol in a test-tube? Write the name of the compound formed during the chemical reaction. Also write chemical equation of the reaction which takes place. 30 Name the functional group of organic compounds that can be hydrogenated. With the help of a suitable example, explain the process of hydrogenation, mentioning the conditions of the reaction and any one change in physical property with the formation of the product. Name any one natural source of organic compounds that are hydrogenated. 31 Name the gas evolved when ethanol reacts with sodium.