Question

Find the pH of a 0.100 M HF solution. Find the percent dissociation of a 0.100 M HF solution Find the pH of a 6.00×10?2 M HF solution. Find the percent dissociation of a 6.00×10?2 M HF solution.

Answer 1

1.

HF = H+ + F-

Ka = [H*][F-]/[HF]

Ka = 3.5*10^-4

[H+] = [F- ] = x

[HF] = 0.100

3.5*10^-4 = (x*x)/(0.100-x)

3.5*10^-5 - 3.5*10^-4x =x^2

X^2 +3.5*10^-4x -3.5*10^-5=0

x= [H+] = 0.00574

p H= -log(0.00574)=2.24

% dissociation = 0.00574 /0.1]*100= 5.74%

2.

HF = H+ + F-

Ka = [H*][F-]/[HF]

Ka = 3.5*10^-4

[H+] = [F- ] = x

[HF] = 6.00×10?2 = 0.06

3.5*10^-4 = (x*x)/(0.06-x)

3.5*10^-5 - 3.5*10^-4x =x^2

X^2 +3.5*10^-4x -2.1*10^-5=0

x= [H+] = 0.0044

p H= -log(0.0044)=2.36

% dissociation = 0.0044/0.06]*100= 7.33%