Question

1) A buffer contains 0.15 mol of propionic acid (C₂H₅COOH) and 0.10 mol of sodium propionate (C₂H₅COONa) in 1.20L. (a) What is the pH of this buffer? (b) What is the pH of the buffer after the addition of 0.01 mol of NaOH? (K_a for C₂H₅COOH is 1.3*10^-5)

2) Using the value of K_sp for Ag₂S (see Appendix D), K_a1 and K_a2 for H₂S (see Appendix D), and K_f = 1.1*10⁵ for AgCl₂^-, calculate the equilibrium constant for the following reaction:

Ag₂S (s) + 4Cl^- (aq) + 2H⁺ (aq) ↔ 2AgCl₂^- (aq) + H₂S (aq)

3) Suppose that a 10 mL sample of a solution is to be tested for I^- ion by addition of 1 drop (0.2 mL) of 0.10 M Pb(NO₃)₂. What is the minimum number of grams of I^- that must be present for PbI₂ (s) to form? (K_sp for PbI₂ is 1.4*10^-8)

Answer 1