7. Redox reactions — Chemistry STD 11 Science — Question

$C{r_2}{O_7}^{2 - } + F{e^{2 + }} + {C_2}{O_4}^{2 - } \to C{r^{3 + }} + F{e^{3 + }} + C{O_2}$

$C{r_2}{O_7}^{2 - } \to 2C{r^{3 + }}$

On balancing

$14{H^ + } + C{r_2}{O_7}^{2 - } + 6{e^ - } \to 2C{r^{3 + }} + 7{H_2}O.....(i)$

$F{e^{2 + }} \to F{e^{3 + }} + {e^ - }.....(ii)$

${C_2}{O_4}^{2 - } \to 2C{O_2} + 2{e^ - }.....(iii)$

On adding all the three equations.

$C{r_2}{O_7}^{2 - } + F{e^{2 + }} + {C_2}{O_4}^{2 - } + 14{H^ + } + 3{e^ - }$ $ \to 2C{r^{3 + }} + F{e^{3 + }} + 2C{O_2} + 7{H_2}O$

Hence the total no. of electrons involved in the reaction $=3$