Question

Calculate the degree of ionization of 0.05 M acetic acid If its pK_a value is 4.74. How is the degree of dissociation affected when its solution also contains

1. 0.01 M 

2. 0.1 M HCI

Answer 1

PK_a = i.e., – log K_a = 4.74 

or log K_a = 4 . 74 = 5.26 

K_a = 1.82 x 10^-5  

In presence of HCI, due to high concentration of H⁺ ion, dissociation equilibrium will shift backward, Le., dissociation of acetic acid will decrease. 

1. In presence of 0.01 M HCI, if x is the amount dissociated, then

2. In the presence of 0.1 M HCl, if y is the amount of acetic acid dissociated, then at equilibrium