Question

Aqueous solution of $K_{2}C{r}_2{O}_7$ (orange) changes to yellow on addition of an alkali. This is because of the formation of:

• A. $C{r}^{6+}$
• B. $Cr{O}_4^{2-}$
• C. $C{r}_2{O}_7^{2-}$
• D. none of the above

Answer 1

Answer: (B)

$Cr{O}_4^{2-}$

Orange coloured dichromate solution reacts with alkali to form yellow coloured chromate.

The reaction is as follows:

$\underset{orange}{C{r}_2{O}_7^{2-}}+2O{H}^{-}\to 2\underset{yellow}{Cr{O}_4^{2-}}+H_{2}O$