Question

Two different salts $\left(A\right)$ [zinc nitrate] and $\left(B\right)$ [potassium bromide] were separately warmed with $conc.H_{2}S{O}_4$. Which of them will produce reddish brown fumes that dissolve in $C{S}_2$ giving yellow solution ?

• A. Both $\left(A\right)$ and $\left(B\right)$
• B. Only $\left(A\right)$
• C. Only $\left(B\right)$
• D. Neither $\left(A\right)$ nor $\left(B\right)$

Answer 1

Answer: (C)

Only $\left(B\right)$

If concentrated sulphuric acid is poured in a bromide solution, first a reddish brown solution is formed, later reddish-brown vapours of bromine accompany the hydrogen bromide.

$2KBr+H_{2}S{O}_4\to K_{2}S{O}_4+2HBr\uparrow$

$2HBr+H_{2}S{O}_4\to 2H_{2}O+S{O}_2\uparrow \underset{Reddish-brown}{+B{r}_2\uparrow }$
$C{S}_2+B{r}_2\to \underset{Yellowcolour}{CB{r}_4}+S_{2}B{r}_2$
Only B produces reddish-brown fumes.