According to Faraday's first law of electrolysis, the mass of the substance deposited or liberated is directly proportional to charge passed through the circuite.

$\mathrm{W}=\frac{\mathrm{Eit}}{96500}$

$\mathrm{E} =$Equivalent weight

$\mathrm{i}=$current in amperes

$\mathrm{t}=$time in seconds

$$\begin{gathered} 0.96=\frac{\mathrm{E}\times 1.2\times 40\times 60}{96500} \\ \Rightarrow \mathrm{E}\simeq 31.75 \end{gathered}$$