Question

What is the time required to deposit one millimole of aluminium by passage of 9.65 ampere through aqueous solution of aluminium ions?

• A. 30 sec
• B. 100 sec
• C. 10 sec
• D. 300 sec

Hint:

Always convert Faradays into coulombs before using \(Q = It\).

Answer 1

The Correct Option is A

Step 1: Write the electrode reaction.
\[ \mathrm{Al^{3+} + 3e^- \rightarrow Al} \]
Step 2: Calculate charge required.
1 mole of Al requires 3 Faradays.
1 millimole of Al requires \(3 \times 10^{-3}\) Faraday.
\[ Q = 3 \times 10^{-3} \times 96500 = 289.5\ \text{C} \]
Step 3: Use relation \(Q = It\).
\[ t = \frac{Q}{I} = \frac{289.5}{9.65} \]
\[ t = 30\ \text{sec} \]
Step 4: Conclusion.
Time required is 30 seconds.