Question

The oxidation state of chromium in the final product formed in the reaction between $KI$ and acidified potassium dichromate solution is:

• A. $+4$
• B. $+6$
• C. $+2$
• D. $+3$

Answer 1

The correct option is D $+3$

$K_{2}C{r}_2{O}_7+7H_{2}S{O}_4+6KI⟶C{r}_2(S{O}_4{)}_3+3I_2+7H_{2}O+4K_{2}S{O}_4$

The reaction between $KI$ and acidified dichromate solution (shown as half cell reactions) is as follows:

$6e^{-}+{Cr}_2{O}_7^{2-}⟶2{Cr}^{3+}$

$2I^{\ominus }⟶I_2+2e^{-}$

The oxidation state of $Cr=+3$ in the product.