試題詳解

3. Hydrogen cyanide gas (HCN), a powerful respiratory inhibitor, is highly toxic. It is a very weak acid (K_a =6.2 ×10^-10) when dissolved in water. If a 50.0 mL sample of 0.100M HCN is titrated with 0.100 M NaOH, calculate the pH of the solution at the equivalence point of the titration.
(A) pH=3.05
(B) pH=8.49
(C) pH=9.21
(D) pH=10.95
(E) pH=11.36