Question

Which of the following is not formed when $H_{2}S$ reacts with acidic $K_{2}C{r}_2{O}_7$ solutions?

• A. $K_{2}S{O}_4$
• B. $C{r}_2(S{O}_4{)}_3$
• C. $S$
• D. $CrS{O}_4$

Answer 1

The correct option is D $CrS{O}_4$

$K_{2}C{r}_2{O}_7+H_{2}S\to C{r}_2(S{O}_4{)}_3+S+K_{2}S{O}_4+H_{2}O$

The oxidation number of chromium changes from +6 to +3, not to 2! so $CrS{O}_4$ cannot be formed.