A student mixes 50.0 mL of 0.20 M acetic acid (CH3COOH) with 50.0 mL of 0.20 M sodium acetate (CH3COONa). The pKa of acetic acid at 25 °C is 4.74. What is the pH of the resulting solution (assume volumes are additive)?
a) 5.04
b) 3.74
c) 4.74
d) 5.74