1) pKa of a weak acid (HA) and pKb of a weak base (BOH) are 3.2 and 3.4 respectively. The pH of their salt (AB) solution is A) 7.2 B) 6.9 C) 7.0 D) 1.0 Answer: Option BExplanation:For a salt of the weak acid and weak base. $pH= 7+\frac{1}{2}pK_{a}-\frac{1}{2}pK_{b}$ Given, $pK_{a}(HA)= 32,pK_{a}(BOH)=3.4$ $\therefore$ $pH =7+\frac{1}{2}(3.2)-\frac{1}{2}(3.4)$ =7+1.6-1.7 = 6.9
