Question

Concentrated sulphuric acid cannot be used to prepare $HBr$ from $NaBr$ because it :

• A. reacts slowly with $NaBr$
• B. oxidises $HBr$
• C. reduces $HBr$
• D. none of the above

Answer 1

The correct option is B oxidises $HBr$

$HBr$ cannot be produced from $NaBr$ using conc. $H_{2}S{O}_4$ because $HBr$ is a strong reducing agent and reduces $H_{2}S{O}_4$ to $S{O}_2$ and itself gets oxidised to $B{r}_2$. The reactions are given below:

$NaBr+H_{2}S{O}_4\to HBr+NaHS{O}_4$
$H_{2}S{O}_4+2HBr\to S{O}_2+B{r}_2+2H_{2}O$