The first step is to calculate the molarity of each compound: final volume of solution = 157 + 139 = 296 mL molarity of nac2h3o2 = (157 x 0.35) / 296 = 0.1856 molar molarity of hc2h3o2 = (139 x 0.46) / 296 = 0.216 molar
Then, we calculate the pH as follows: pKa of acetic acid = -log(1.75 × 10^-5) = 4.7569 pH = pKa + log ([salt] / [acid]) = 4.7569 + log(0.1856 / 0.216) = 4.691