Ch.16 - Aqueous Equilibria: Acids & Bases
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- We’ve said that alkali metal cations do not react appreciably with water to produce H3O+ ions, but in fact, all cations are acidic to some extent. The most acidic alkali metal cation is the smallest one, Li+, which has Ka = 2.5 * 10^-14 for the reaction: Li(H2O)4+ (aq) + H2O (l) ⇌ H3O+ (aq) + Li(H2O)3(OH) (aq). This reaction and the dissociation of water must be considered simultaneously in calculating the pH of Li+ solutions, which nevertheless have pH ≈ 7. Check this by calculating the pH of a 0.10 M LiCl solution.
Problem 157
Problem 158a
A 1.000 L sample of HF gas at 20.0 °C and 0.601 atm pressure was dissolved in enough water to make 50.0 mL of hydrofluoric acid. (a) What is the pH of the solution?
Problem 158b
A 1.000 L sample of HF gas at 20.0 °C and 0.601 atm pressure was dissolved in enough water to make 50.0 mL of hydrofluoric acid. (b) To what volume must you dilute the solution to triple the percent dissociation?
- A 200.0 mL sample of 0.350 M acetic acid (CH3CO2H) was allowed to react with 2.000 L of gaseous ammonia at 25 °C and a pressure of 650.8 mm Hg. Assuming no change in the volume of the solution, calculate the pH and the equilibrium concentrations of all species present (CH3CO2H, CH3CO2-, NH3, NH4+, H3O+, and OH-). Values of equilibrium constants are listed in Appendix C.
Problem 159