Calculate the pH after 0.018 mole of HCl is added to 1.00 L of each of the four solutions. (Assume that all solutions are at 25°C.) (a) 0.129 M acetic acid (HC2H3O2, Ka = 1.8 ✕ 10−5) (b) 0.129 M sodium acetate (NaC2H3O2) (c) pure H2O (d) 0.129 M HC2H3O2 and 0.129 M NaC2H3O2