Question

Consider the reaction : $C{r}_2{O}_7^{2-}+14H^{+}+6e^{-}\to 2C{r}^{3+}+7H_{2}O$

What is the quantity of electricity in coulombs needed to reduced $1mol$ of $C{r}_2{O}_7^{2-}$?

• A. $6\times {10}^{6}C$
• B. $5.79\times {10}^{5}C$
• C. $5.25\times {10}^{5}C$
• D. None of these

Answer 1

Answer: (B)

$5.79\times {10}^{5}C$

$C{r}_2{O}_7^{2-}+14H^{+}+6e^{-}\to 2C{r}^{3+}+7H_{2}O$

The valency factor for Chromium is $6$.

Applying faraday's first law-

$\frac{Q}{F}=mole\times V.f.$

$Q=mole\times V.f.\times F$

$Q=1\times 6\times 96500$

$Q=5.79\times {10}^{5}C$