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Electrochemistry

Question
CBSEENCH12006099

The conductivity of 0.01 M solution of acetic acid at 25°C is 1.63 x 10–4 s cm–1. Given:
Λ°m (HCl) = 426 s cm2 mol–1, Δ°m (Na AC) = 91.5 cm2 mol–1
Λ°m (NaCl) = 126.5 cm2 mol–1 Calculate:
(a) the molar conductivity of acetic acid
(b) the degree of dissociation of acetic acid.
(c) the dissociation constant.
 (d) the pH of 0.01 M solution of acetic acid.

 

Solution

a) The molar conductivity of acetic acid given by;

Λm =103kM    =103 x1.63x10-40.01=16.3 S cm2mol-1b) The degree of dissociation (α) is α =ΛmΛm0Λm0 =Λm0(HCl) +Λm0(NaAc) -Λm0(NaCl)   =426 +91-126 =391S cm2 Mol-1Therefore α =ΛmΛm0 =16.3391 =0.042c) K=21-α = 0.01 x(0.042)21-0.042 =1.84 x 10-5d) [H+] =Cα =0.01 x0.042=4.2 x10-4MpH =-log [H+] =-log(4.2 x10-4) =3.38