In the presence of hydroxide ion, a sulphate ion ________ oxidised .

Explanation

To solve the question "In the presence of hydroxide ion, a sulphate ion ________ oxidised," we need to analyze the behavior of the sulfate ion (SO₄²⁻) when hydroxide ions (OH⁻) are present.

### Step-by-Step Solution:

1. **Identify the Ions Involved**:
- We have two ions: hydroxide ion (OH⁻) and sulfate ion (SO₄²⁻).

2. **Understand Oxidation and Reduction**:
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