Question

How many Coulombs are required to oxidise 0.1 mole of H₂O to oxygen?

• A. 1.93 × 10⁵ C
• B. 1.93 × 10⁴ C
• C. 3.86 × 10⁴ C
• D. 9.65 × 10³ C

Hint:

The hint involves Faraday's laws of electrolysis to calculate the charge required for a given amount of substance.

Answer 1

The Correct Option is B

To determine how many Coulombs are required to oxidize 0.1 mole of H₂O to oxygen, we follow these steps:

1. First, consider the balanced chemical reaction for the oxidation of water to produce oxygen gas:

\[ 2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4\text{e}^- \] 

1. This equation shows that 2 moles of water produce 1 mole of oxygen gas, releasing 4 moles of electrons. Therefore, for the oxidation of 2 moles of water, 4 moles of electrons are needed.
2. We need to determine the number of electrons required to oxidize 0.1 mole of water. Since 4 moles of electrons are required for 2 moles of H₂O, for 0.1 mole of H₂O, the moles of electrons required are:

\[ \text{Moles of electrons} = 0.1 \times \left(\frac{4}{2}\right) = 0.2 \text{ moles of electrons} \]

1. Next, we'll convert the moles of electrons to Coulombs using Faraday's constant, which is approximately 96,500 C/mol. Thus, the charge in Coulombs is:

\[ \text{Charge (C)} = 0.2 \text{ moles} \times 96500 \text{ C/mole} = 19300 \text{ C} \]

1. Therefore, the number of Coulombs required to oxidize 0.1 mole of H₂O to oxygen is \(1.93 \times 10^4 \text{ C}\).

This corresponds to the option 1.93 × 10⁴ C, which is the correct answer.