Question

The amount of current in Faraday is required for the reduction of 1 mol of $C{r}_2{O}_7^{2-}$ ions to $C{r}^{3+}$ is,

• A. 1 F
• B. 2 F
• C. 6 F
• D. 4 F

Answer 1

Answer: (C)

$\underset{(+C)}{C{r}_2}{O}_7^{2-}⟶\underset{(+3)}{C{r}^{3+}}:$ Oxidation number of $Cr$

It shows change in oxidation number, i.e. change of 3 moles of electrons per mole of Cr-atom.

$\because C{r}_2{O}_7^{2-}$ has 2 moles of Cr-atoms. Hence, total 6 moles of electrons, i.e. $6F$ of charge (current) is required for reduction of 1 mole of $C{r}_2{O}_7^{2-}$ ions.