Calculating the pH of a weak acid titrated with a strong b. An analytical chemis

Question

Calculating the pH of a weak acid titrated with a strong b. An analytical chemist is titrating 155.0 mL of a 0.8300 M solution of nitrous acid (HNO2) with a 0.5600 M solution of NaOH. The pK, of nitrous acid is 3.35. Calculate the ph of the acid solution after the chemist has added 133.7 mL of the Na0H solution to it. Note for advanced students: you may assume the final volume equals the initial volume of the solution plus the volume of NaOH solution added. Round your answer to 2 decimal places. PH- Explanation Check

Explanation / Answer

Since the mixture is an example acidic buffer

PH = pKa +log(moled)salt /(Moles )acid

HNO2 + NaoH - - - - - > Nano2 + H2O

no of moles of HNO2 = 155x0.83=128.65

No of moles of NaOH + 133.7x.56=74.8

No of moles of salt = 74.8 & and acid left, 128.65-74.8=53.8 mol

PH =3.35+ log (74.8/53. 7)

=3.35+log(1.39)

=3.35+0.14

PH = 3.49

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