Question

$H_{2}S$ gas is not evolved when $S{O}_3^{2-}$ ion reacts with folIowing reagents.

• A. $Zn+dil.H_{2}S{O}_4$
• B. $Al+$ conc. $NaOH$
• C. $Al+$ dil. $HCl$
• D. None of these

Answer 1

Answer: (B)

$Al+$ conc. $NaOH$

$S{O}_2-+2Al+2O{H}^{-}+3H_{2}O\to S^{2-}+2\left[Al\right(O{H}_4){]}^{-}$

$H_{2}S$ gas is not evolved because liberated $H_{2}S$ is neutralized by $NaOH$ and $N{a}_{2}S$ is formed.