An inorganic compound A is dissolved in dilute hydrochloric acid and is then warmed. A colourless gas B is produced. When a filter paper moistened with potassium iodate and the starch solution is exposed to the gas it turns blue. The gas B and the compound A are:

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$H_{2} S$ and ${Na}_{2} S$

$H_{2} S$ and ${Na}_{2} {SO}_{3}$

${SO}_{2}$ and ${Na}_{2} {SO}_{3}$

${SO}_{3}$ and ${Na}_{2} {SO}_{4}$

answer is A.

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Detailed Solution

When sulphate is dissolved in dilute hydrochloric acid and is then warmed $N a_{2} S O_{3}$ gas is produced.

${Na}_{2} {SO}_{3} + 2 Hcl ⟶ {SO}_{2} + 2 Nacl + H_{2} O$

Ozone turns blue when it comes into touch with starch-iodide (Schoenlein paper) paper. Because ozone acts as an oxidizing agent and causes iodide to oxidize into iodine.

Hence the correct option is A.

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