(a) When ethanoic acid reacts with sodium hydrogen carbonate, then a salt X is formed and a gas Y is evolved.
Name the salt X and gas Y. Describe an activity with the help of a labelled diagram of the apparatus used to prove that the evolved gas is the one which you have named. Also write the chemical equation of the reaction involved.
(b) Give any two uses of ethanoic acid.
(a) Salt X is sodium ethanoate, CH3COONa; Gas Y is carbon dioxide, CO2
Activity: Take a boiling tube and put about 0.5 g of sodium carbonate in it. Add 2 ml of dilute ethanoic acid to the boiling tube (through a thistle funnel). We will observe that brisk effervescence of carbon dioxide gas is produced. Let us pass this gas through lime water taken in a test tube. We will find that lime water turns milky. Only carbon dioxide gas can turn lime water milky. So, this experiment proves that when ethanoic acid reacts with sodium carbonate, then carbon dioxide gas is evolved.
CH3COOH + NaHCO3 → CH3COONa + CO2 ↑+ H2O
(b)(i) Dilute ethanoic acid (in the form of vinegar) is used as a food preservative in the preparation of pickles and sauces.
(ii) It is used in the manufacture of acetone and esters used in perfumes.
(a) Activity:
(i) Take 1 ml of pure ethanol (absolute alcohol) in a test-tube and add 1 ml of glacial ethanoic acid to it. Then add 2 or 3 drops of concentrated sulphuric acid to the mixture.
(ii) Warm the test-tube containing above reaction mixture in hot water bath (a beaker containing hot water) for about 5 minutes.
(iii) Pour the contents of the test-tube in about 50 ml of water taken in another beaker and smell it.
(iv) A sweet smell is obtained indicating the formation of an ester.
Reaction:
(c) Uses of esters:
(i) Esters are used in making artificial flavours and essences. These are used in cold drinks, ice-creams, sweets and perfumes.
(ii) Esters are used as solvents for oils, fats, gums, resins, cellulose, paints, varnishes, etc.