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Question:

In a basic buffer, 0.0025 mole of NH4Cl and 0.15 mole of NH4OH are present. The pH of the solution will be: (pKa) = 4.74

5.48

6.62

11.04

10.24

Solution:

From Henderson's equation,
pOH = pKb + log[salt]/[base] = 4.74 + log(0.0025/0.15) = 4.74 + log(1/60) = 2.96
pH = 14 - 2.96 = 11.04