The limiting currect (in $\mu \mathrm{A}$ ) from the reduction of $3 \times 10^{-4} \mathrm{M} \mathrm{Pb}^{2+}$, using a dropping mercury electrode (DMF) with characteristics, $\mathrm{m}=3.0 \mathrm{mg} \mathrm{s}^{-1}$ and $\mathrm{t}=3 \mathrm{s}$, is (diffusion coefficient of $\mathrm{Pb}^{2+}=1.2 \times 10^{-5} \mathrm{cm}^{2} \mathrm{s}^{-1}$ ) ____.
Answer
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