Question

stoichometric point = 22 ml

Using the initial concentrations of NaCH₃COO and HCl, and a reliable literature value for the pKb for NaCH₃COO (or pKa for CH₃COOH), predict the theoretical pH of the stoichiometric point. Show all calculations in your report.

Concentration of HCl=0.10 M , Concentration of sodium acetate =0.22 M

Answer 1

pKb for Acetic acid --> 14-4.75 = 9.25

find theoretical pH in stoichiometric point:

NaCH3COO + HCl --> NaCl + CH3COOH

concentration of acid = 0.1 M

volume of acid = 22 mL

mmol of acid = MV = 0.1*22 = 2.2 mmol

so..

mmol of acetate = 2.2 mmol

V = mmol/M = 2.2/0.22 = 10 mL ofa cetate solution

total Volume in equivalence point = V1+V2 = 22+10 = 32 mL

[acetate] = 2.2/32 = 0.06875 M

so..

NaCH3COO + HCl --> NaCl + CH3COOH

then

CH3COOH <-> CH3COO- + H+

Ka = [CH3COO-][H+]/[CH3COOH]

Ka = 10^-4.75

1.8*10^-5 = x*x/(0.06875 -x)

x = 0.001103

[H+] = x = 0.001103

pH = -log(0.001103 =2.95742