Question

The following equations are balanced atomwise and chargewise.
(i) $C{r}_2{O}_7^2+8H^{+}+3H_2{O}_2\to 2C{r}^{3+}+7H_{2}O+3O_2$
(ii) $C{r}_2{O}_7^2+8H^{+}+5H_2{O}_2\to 2C{r}^{3+}+9H_{2}O+4O_2$
(iii) $C{r}_2{O}_7^2+8H^{+}+7H_2{O}_2\to 2C{r}^{3+}+11H_{2}O+5O_2$
The precise equation/equations representing the oxidation of $H_2{O}_2$ is/are :

• A. (i) only
• B. (ii) only
• C. (iii) only
• D. all the three

Answer 1

The correct option is A (i) only

The reactions are as follows:
$6e^{-}+14H^{+}+C{r}_2{O}_7^{2-}\to 2C{r}^{3+}+7H_{2}O$
$3H_2{O}_2\to 3O_2+6H^{+}+6e^{-}$
$C{r}_2{O}_7^{2-}+8H^{+}+3H_2{O}_2\to 2C{r}^{3+}+7H_{2}O+3O_2$
Therefore, only (i) is correct.