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1. ⇒ (MHT CET 2023 12th May Morning Shift )

Electrolytic cells containing $Zn$ and $Al$ salt solutions are connected in series. If $6.5 g$ of $Zn$ is deposited in one cell calculate mass of $Al$ deposited in second cell (molar mass : $Zn = 65, Al = 27$ ) by passing definite quantity of electricity?

A. 2.4 g

B. 2.1 g

C. 2.7 g

D. 1.8 g

Correct Option is (D)

Cell 1:

$\begin{aligned} {Zn}_{(sq)}^{2 +} + 2 e^{-} ⟶ {Zn}_{(s)} \\ (mole ratio))_{1} = \frac{1 mol}{2 {mole}^{-}} \end{aligned}$

Cell 2:

$\begin{aligned} {Al}_{(aq)}^{3 +} + 3 e^{-} ⟶ {Al}_{(s)} \\ (mole ratio)_{2} = \frac{1 mol}{3 {mole}^{-}} \end{aligned}$

$\begin{aligned} \frac{W_{1}}{(mole ratio)_{1} \times M_{1}} = \frac{W_{2}}{(mole ratio)_{2} \times M_{2}} \\ \frac{6.5 g}{1 mol / 2 mol e^{-} \times 65 g {mol}^{- 1}} \\ = \frac{W_{2}}{1 mol / 3 mol e^{-} \times 27 g {mol}^{- 1}} \\ \frac{6.5 g \times 2}{65} = \frac{W_{2} \times 3}{27} \\ W_{2} = \frac{6.5 \times 2 \times 27}{65 \times 3} = 1.8 g \end{aligned}$

⇒Electrochemistry