Question

Henderson-Hasselbach solution check, gen chem stuff

Answer 1

Calculate the change in pH when 7.00 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).

given Kb of NH3 = 1.8×10^(–5)

Answer 2

my attempt:

HCl + NH3 ---> NH4+ + Cl-

Ka of NH4 = 10^(-14) / (1.8×10^(–5)) = 5.56 * 10^(-10)

Henderson eq: pKa + log(NH3/NH4+)

initial conditions:

-log( 5.56 * 10^(-10)) = 9.255

after acid is added = 9.255 + log[ (0.01 + (7/1000)*0.1) / (0.01 - (7/1000)*0.1))