Question

How many electrons lost or gained by Cr?
$C{r}_2{O}_7^{2-}\to C{r}^{3+}$

• A. 5
• B. 4
• C. 2
• D. 6

Answer 1

The correct option is D 6

Let’s go step by step here.
First multiply $C{r}^{3+}x2$ to balance number of Cr atoms.

Therefore, $6e^{-}+C{r}_2{O}_7^{2-}\to 2C{r}^{3+}$