Question

When electricity is passed through a solution of ${\mathrm{AlCl}}_3$, $13.5\mathrm{g}$ of $\mathrm{Al}$ is discharged. The amount of charge passed is __________.

• A. $1.5\mathrm{F}$
• B. $0.5\mathrm{F}$
• C. $1.0\mathrm{F}$
• D. $2.0\mathrm{F}$

Answer 1

The correct option is A

$1.5\mathrm{F}$

Explanation for correct option:

(A) $1.5\mathrm{F}$

Step 1: Electron transfer reaction:

• When electricity is passed through ${\mathrm{AlCl}}_3$ solution, ${\mathrm{Al}}^{3+}$the will accept three electrons from the solution and discharge as $\mathrm{Al}$.

${\mathrm{Al}}^{{}^{3+}}+3{\mathrm{e}}^{-}\to \mathrm{Al}$

Step 2: Finding the number of moles:

• Finding the number of moles of aluminium we get,

$$\begin{gathered} \mathrm{Moles}\mathrm{of}\mathrm{Al}=\frac{\mathrm{Number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{solute}\mathrm{taken}}{\mathrm{Total}\mathrm{number}\mathrm{of}\mathrm{moles}\mathrm{in}\mathrm{solution}} \\ =\frac{13.5}{27} \\ =0.5 \end{gathered}$$

Step 3: Finding the number of moles of electrons required:

• The number of moles of electrons required to discharge $\mathrm{Al}$

$\mathrm{Number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{electrons}\mathrm{required}=\mathrm{n}\mathrm{x}\mathrm{moles}\mathrm{of}\mathrm{Al}$

$$\begin{gathered} =3\mathrm{x}0.5(\mathrm{Where}\mathrm{n}=\mathrm{number}\mathrm{of}\mathrm{electrons}) \\ =1.5\mathrm{F} \end{gathered}$$

Explanation for incorrect option:

Since the correct option is $1.5\mathrm{F}$. Therefore, options (B), (C) & (D) are incorrect.

Therefore, the correct option is (A) $1.5\mathrm{F}$.