Question

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 below.

1. What will be the action of gas on
   1. dry litmus paper?
   2. moist litmus paper?
2. Write a balanced chemical equation for the reaction taking place.

Answer 1

1. 1. There will be no action on dry litmus paper.
   2. Litmus paper turns red because sulphur is a nonmetal, and the oxides of nonmetals are acidic. On prolonged contact with the gas, the litmus paper becomes decolourised.
2. \[\ce{S_{(s)} + O2_{(g)} ->[\Delta] SO2_{(g)}}\]
   \[\ce{SO2_{(g)} + H2O_{(l)} -> \underset{(turns moist blue litmus red)}{H2SO3_{(aq)}}}\]