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  4. MnO 2 is prepared by electrolysis of aqueous solution of MnSO 4, as per reaction Mn 2+(a q)+2 H 2 O arrow MnO 2(s)+2 H (a q)++ H 2(g) Passing a current of 25 A for 30 hours gives one kg of MnO 2 . What is the current efficiency? (Mol. wt. of MnO 2 =87)

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Q. $MnO _{2}$ is prepared by electrolysis of aqueous solution of $MnSO _{4}$, as per reaction $Mn ^{2+}_{(a q)}+2 H _{2} O \rightarrow MnO _{2(s)}+2 H _{(a q)}^{+}+ H _{2(g)}$ Passing a current of $25 A$ for 30 hours gives one $kg$ of $MnO _{2} .$ What is the current efficiency? (Mol. wt. of $MnO _{2}$ $=87)$

Electrochemistry

Solution:

Applying, $w=Z \times I \times t$

$w=1 \,kg =1000 \,g , I=$ current required, $t=30\, hr =30 \times 3600\, s$

$I=\frac{1000 \times 2 \times 96500}{87} \times \frac{1}{30 \times 3600}=20.54$ ampere

Current efficiency $=\frac{20.54}{25} \times 100=82.16 \%$