Question

If acidified solution of $K_2{Cr}_2{O}_7$ turns green on addition of a salt then salt may contain :

• A. $F{e}^{2+}$
• B. $K^{+}$
• C. $M{n}^{2+}$
• D. $H^{+}$
• E. None

Answer 1

The correct option is A $F{e}^{2+}$

In acidic medium, ${Fe}^{2+}$ is oxidized to ${Fe}^{3+}$ and ${Cr}_2{O}_7^{2-}$ is reduced to chromate. Henc, the colour changes from orange to green.

$6F{e}^{2+}+C{r}_2{O}_7^{2-}+14H^{+}\to 6F{e}^{3+}+2C{r}^{3+}\left(green\right)+7H_{2}O$

Thus, the given statement, "If acidified solution of $K_2{Cr}_2{O}_7$ turns green on addition of a salt then salt may contain ${Fe}^{2+}$." is true.

Hence, option A is correct.