135 g of water is electrolysed during an experiment. If the efficiency of current is 75% then select the correct statement
 

H₂O $\to$H₂ + $\frac{1}{2}$O₂

1 mol of H₂​O forms 1 mol of H₂​ and $\frac{1}{2}$ mol of O₂

So, moles of H₂O = $\frac{135}{18}$ = 7.5 mol, moles of H₂ is also 7.5 mol and moles of O₂ is $\frac{7.5}{2} \mathrm{mol}.$

If one mole of water requires 2 F of electrons, then Faraday requires for 7.5 mol of water:

$\mathrm{Amount} \mathrm{of} \mathrm{Faraday}=\frac{2 \mathrm{F}}{1 \mathrm{mol}}\times 7.5 \mathrm{mol}=15 \mathrm{F}$

But efficiency is given as 75%, therefore the total electricity consumed (x) is:

$$\begin{gathered} \mathrm{x}\times \frac{75}{100}=15 \mathrm{F} \\ \mathrm{x}=20 \mathrm{F} \end{gathered}$$