Question

100 ml of 0.02 m benzoic acid is titrated using 0.02 naoh , ph after 100 ml

Answer 1

This is quite simple, first calculate the number of moles in each case,

Number of moles = 100 x 0.02/1000

                              = 0.002 moles.

Being that the details are the same this means that both benzoic acid and sodium hydroxide have similar number of molecules = 0.002 moles

Total volume is = 100 + 100 = 200 ml

so the concentration= 0.002/200

                                   = 1.0 x 10^-5 M

ka of benzoic acid = 6.4 x 10^-5

degree of ionisation = √6.4 x 10^-5/1.0 x 10^-5

                                 = 2.5 x 10^-5

equilibrium concentration =2.5 x 10^-5 x (1.0 x 10^-5)

                                            = 2.5 x 10^-10

               pOH= -log 2.5 x 10^-10

                   pOH= 9.6

                     pH= 4.4