Question

Assertion :$S{O}_2$ turns acidified $K_{2}C{r}_2{O}_7$ green. Reason: $K_{2}C{r}_2{O}_7$ is reduced to $C{r}^{3+}$ (green) salt by $S{O}_2$.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Both Assertion and Reason are incorrect.

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.

Sulphur dioxide is oxidized to sulphuric acid. Potassium dichromate is reduced to chromic sulphate. Orange colour of solution turns green.

$K_{2}C{r}_2{O}_7$ + $3S{O}_2$ + $H_{2}S{O}_4$ $\to$ $K_{2}S{O}_4$ + $C{r}_2(S{O}_4{)}_3$ + $H_{2}O$

$S{O}_2$ reduces orange coloured $K_{2}C{r}_2{O}_7$ to green colour $C{r}^{3+}$.

Hence, $S{O}_2$ turns acidified $K_{2}C{r}_2{O}_7$ green.

Thus, both Assertion and Reason are correct and Reason is the correct explanation for Assertion.