a Calculate the change in pH when 500 mL of 0100 M HCLaq is

(a) Calculate the change in pH when 5.00 mL of 0.100 M HCL(aq) is added to 100.0 mL of a buffer solution that is 0.100 M in NH3(aq) and 0.100 M in NH4Cl(aq)

(b) Calculate the change in pH when 5.00 mL of 0.100 M NaOH(aq) is added to the original buffer solution

Solution

1)pH=14-(pKb+log(salt/acid)

intial,

pH=14-(4.75+log(0.1/0.1))

=9.25

final

pH=14-(4.75+log((100*0.1+5*0.1)/(100*0.1-5*0.1)))

=9.2

so change=9.2-9.25

=-0.05

b)intial,

pH=14-(4.75+log(0.1/0.1))

=9.25

final

pH=14-(4.75+log((100*0.1-5*0.1)/(100*0.1+5*0.1)))

=9.293

so change=9.293-9.25

=0.043