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Given: [NH₃] = 0.3 M, [NH₄⁺] = 0.2 M, Kb = 1.8 × 10⁻⁵ pOH = pKb + log [salt]/[base] pOH = 4.74 + log 0.2/0.3

1. 4.74
2. 4.56
3. 9.436
4. None of these

Correct answer: 4.56

Solution

Using the formula pOH = pKb + log([salt]/[base]), we calculate pOH = 4.74 + log(0.2/0.3) = 4.74 + log(2/3) = 4.74 - 0.176 = 4.56.

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