Question

pH of the Buffer after the addition of strong base

Original buffer solution=
50.0 mL of 1.0 M CH3COOH
50.0 mL of 1.0 M NaCH3COO

Take 50.0 mL of this buffer solution and add 2.0 mL of 1.0 M NaOH

Calculate the expected pH of this solution.

Answer 1

no of moles of CH3COOH = molarity * volume in L

                                             = 1*0.05   = 0.05 moles

no of moles of CH3COONa   = molarity * volume in L

                                               = 1*0.05 = 0.05 moles

By the addition of 2 ml of 1 M NaOH

    no of moles of NaOH   = molarity * volume in L

                                         = 1*0.002   = 0.002moles

no of moles of CH3COOH by the after addition of 0.002 moles of NaOH = 0.05-0.002   = 0.048 moles

no of moles of CH3COONa by the after addition of 0.002 moles of NaOH   = 0.05+ 0.002   = 0.052 moles

             PH   = PKa + log[CH3COONa]/[CH3COOH]

                      = 4.75 + log0.052/0.048

                      = 4.75 + 0.0347   = 4.7847 >>>>>answer