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 the figure here.
(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.
(a) When sulphur is burnt in air, then sulphur dioxide(SO2) gas is formed.
(i) There will be no action on dry litmus paper.
(ii) Sulphur dioxide gas turns moist blue litmus paper to red.
(b) S (s) + O2 (g) 
SO2 (g)
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