Question

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

(a) 0.01 M 

(b) 0.1 M in HCl? 

Answer 1

When HCl is added to the solution, the concentration of H+ ions will increase. Therefore, the equilibrium will shift in the backward direction i.e., dissociation of acetic acid will decrease. 

Case I: When 0.01 M HCl is taken. 

Let x be the amount of acetic acid dissociated after the addition of HCl. 

As the dissociation of a very small amount of acetic acid will take place, the values i.e., 0.05 – x and 0.01 + x can be taken as 0.05 and 0.01 respectively. 

Case II: When 0.1 M HCl is taken. 

Let the amount of acetic acid dissociated in this case be X. As we have d