O ACIDS AND BASES Calculating the pH of a weak acid titrated with a strong b. An
ID: 1088982 • Letter: O
Question
O ACIDS AND BASES Calculating the pH of a weak acid titrated with a strong b. An analytical chemist is titrating 161.6 mL of a 0.2100 M solution of hydrazolc acd (HN) with a 0.6600 M solution of KOH. The pK, of hydrazoic acid is 4.72. Calculate the pH of the acid solution after the chemist has added 15.90 mL of the KOH solution to it. Note for advanced students: you may assume the final volume equals the initial volume of the solution plus the volume of KOH solution added. Round your answer to 2 decimal places. pHExplanation / Answer
millimoles of HN3 = 161.6 x 0.2100 = 33.936
millimoles of KOH = 15.90 x 0.6600 = 10.494
HN3 + KOH -------------------> KN3 + H2O
33.936 10.494 0 0
23.442 0 10.494
pH = pKa + log [salt / acid]
= 4.72 + log [10.494 / 23.442]
pH = 4.37
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