3. Hydrogen cyanide gas (HCN), a powerful respiratory inhibitor, is highly toxic. It is a very weak acid (Ka =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