How to calculate pH in buffer solution?

A 1.0 L buffer is prepared from 0.25 mol of acetic acid and 0.25 mol of sodium acetate. Calculate the change in pH if 0.15 mol of Hydroxide is formed in the buffer.

thx!How to calculate pH in buffer solution?
initial pH = 4.7 + log 0.25/0.25 = 4.7



CH3COOH + OH- %26gt;%26gt; CH3COO- + H2O

moles acid = 0.25 - 0.15=0.10

moles acetate = 0.25 + 0.15 = 0.40

pKa = 4.7

pH = 4.7 + log 0.40/ 0.10=5.3

change =0.6