Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it as shown in figure below: (a) What will be the action of gas on (i) dry litmus paper ? (ii) moist litmus paper ? (b ) Write a balanced chemical equation for the reaction taking place.

Pratyush took sulphur powder on a spatula and heated it. He collected

1.	Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it as shown in figure below: (a) What will be the action of gas on (i) dry litmus paper ? (ii) moist litmus paper ? (b ) Write a balanced chemical equation for the reaction taking place.
Answer» Solution :When sulphur POWDER is heated in air, it forms sulphur dioxide, which is acidic in nature and its AQUEOUS solution is called sulphurous acid `(H_2SO_3)`. (a) Action of gas : (i) There will be no effect of gas on dry litmus PAPER. (II) Moist blue litmus paper changes its colour to red due to `H^+`ions present in the aqueous solution of `H_2SO_3` formed from `SO_2`obtained after burning sulphur. (b) BALANCED chemical equation for the above activity is as given below: `S(s) + O_2(g)toSO_2(g)` ` SO_2(g) + H_2O(l)underset("Sulphurous acid")(H_2SO_3(aq))`