KCET · Chemistry · Electrochemistry
One litre solution of \( \mathrm{MgCl}_{2} \) is electrolyzed completely by passing a current of \( 1 \mathrm{~A} \) for \( 16 \min 5 \)
sec. The original concentration of \( \mathrm{MgCl}_{2} \) solution was (Atomic mass of \( \mathrm{Mg}=24 \) )
- A \( 0.5 \times 10^{-3} \mathrm{M} \)
- B \( 1.0 \times 10^{-2} \mathrm{M} \)
- C \( 5 \times 10^{-3} \mathrm{M} \)
- D \( 5 \times 10^{-2} \mathrm{M} \)
Answer & Solution
Correct Answer
(C) \( 5 \times 10^{-3} \mathrm{M} \)
Step-by-step Solution
Detailed explanation
(C)
\[
\begin{array}{l}
m=\frac{E I Z}{96500}=\frac{12 \times 1 \times 965}{96500}=12 \times 10^{-2} g \\
\text { Molarity, } M=\frac{w_{2}}{M_{2}} \times \frac{1000}{V_{\text {wat }}}=\frac{12 \times 10^{-2}}{24} \times \frac{1000}{1000} \\
=0.5 \times 10^{-2} M=5 \times 10^{-3} M
\end{array}
\]
\[
\begin{array}{l}
m=\frac{E I Z}{96500}=\frac{12 \times 1 \times 965}{96500}=12 \times 10^{-2} g \\
\text { Molarity, } M=\frac{w_{2}}{M_{2}} \times \frac{1000}{V_{\text {wat }}}=\frac{12 \times 10^{-2}}{24} \times \frac{1000}{1000} \\
=0.5 \times 10^{-2} M=5 \times 10^{-3} M
\end{array}
\]
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