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3. Metals and Non-metals
hard
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.

Option A
Option B
Option C
Option D
Solution
$(a)$ $(i)$ There will be no action on dry litmus paper.
$(ii)$ Since the gas is sulphur dioxide $(SO_2)$, it turns moist blue litmus paper to red because sulphur dioxide reacts with moisture to form sulphurous acid.
$(b)$ ${{S}_{(s)}}\,+\,{{O}_{2(g)}}\,\to \,\underset{\text{ Sulphur dioxide }}{\mathop{S{{O}_{2(g)}}}}\,$
$S{{O}_{2(g)}}\,+\,{{H}_{2}}{{O}_{(l)}}\,\to \,\underset{\text{ Sulphurous acid }}{\mathop{{{H}_{2}}S{{O}_{3(aq)}}}}\,$
Standard 10
Science