Step 1:

The initial amount of [HC₂H₃O₂] is 0.3 mol.

The initial amount of [NaC₂H₃O₂] is 0.3 mol.

The chemical equation is .

pH of the buffer solution when no NaOH is added is 4.74.

.

Now 0.02 mol of NaOH is added.

Initial Amount
Change in Amount
Equilibrium amount			\ \

Step 2:

Concentration of [HC₂H₃O₂] is .

Concentration of [NaC₂H₃O₂] is .

Definition of pH:

pH of the solution is 4.4.79799

Solution:

pH of the solution is 4.79799.