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Calculate the degree of dissociation of 0.1 N acetic acid (CH3COOH) given that its dissociation constant Ka = 1 * 10⁻⁵.

1. 10⁻⁵
2. 10⁻⁴
3. 10⁻³
4. 10⁻²

Correct answer: 10⁻²

Solution

For a weak acid: Ka = C * alpha², so alpha = sqrt(Ka / C) = sqrt(10⁻⁵ / 0.1) = sqrt(10⁻⁴) = 10⁻². Check: 0.01 << 1, so the approximation is valid.

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