Calculate pH of 100 ml solution containing 0.05 g acetic acid and 0.06 g sodium acetate.

General information:
Sodium acetate completely ionizes in solution to produce sodium ions and acetate ions according to the following formula:

NaAcetate_{(in aqueous solution)} → Na⁺_(aq) + Acetate^-_(aq)

Accordingly, the number of moles of acetate ions in solution is equal to that of  sodium acetate. Acetic acid and sodium acetate (acid - conjugare base) in solution compose a buffer system. The pH can be calculated using the buffer equation or using the pH equation for a mixture of an acid with its conjugate base. Molar concentrations must be calculated before using any of these equations.

Molar mass (molecular weight) of acetic acid = 60.05 g/ mole
Molar mass (molecular weight) of sodium acetate = 82.03 g/ mole
Acetic acid has Ka = 1.75 × 10^-5 and pKa = 4.76

Calculations:
Volume of solution in liters = 100 ml × (0.001 liter/ ml) = 0.1 liter
Number of moles of acetic acid in solution = 0.05 g ÷ (60.05 g/ mole) = 0.0008 mole
Molar concentration of acetic acid in solution = 0.0008 mole ÷ (0.1 liter) = 0.008 M
Number of moles of sodium acetate in solution = 0.06 g ÷ (82.03 g/ mole) = 0.0007 mole
Molar concentration of sodium acetate in solution = 0.0007 mole ÷ (0.1 liter) = 0.007 M

Using the buffer equation:
pH = pKa + log ([acetate]/[acetic acid])
pH = 4.76 +  log (0.007/0.008) = 4.76 - 0.06 =4.70

The same answer is obtained using the pH equation for a mixture of an acid with its conjugate base or simply using online pH calculator.

Related posts:
Examples on buffer calculations.
What is buffer capacity.
Factors affecting pH of buffer solutions.