Question

Sulphur powder is burnt in air and the gas evolved (A) is collected in a test tube. (A) is allowed to pass over moist litmus paper where a compound (B) is formed.
Mark the correct answer.

• A. A is $H_2$
  B is $H_{2}S{O}_4$
  Litmus turns red to blue
• B. A is $S{O}_2$
  B is $H_{2}S{O}_4$
  Litmus turns blue to red
• C. A is $S{O}_2$
  B is $H_{2}S{O}_3$
  Litmus turns red to blue
• D. A is $S{O}_2$
  B is $H_{2}S{O}_3$
  Litmus turns blue to red

Answer 1

The correct option is D A is $S{O}_2$

B is $H_{2}S{O}_3$
Litmus turns blue to red
Sulphur powder burnt in air to form sulphur dioxide.
Sulphur dioxide turns moist litmus paper from blue to red as $S{O}_2$ react with water to form sulphurous acid.
$S\left(s\right)+O_2\left(g\right)\to S{O}_2\left(g\right)$
$S{O}_2\left(g\right)+H_{2}O\to H_{2}S{O}_3$