Schedule Today (2/25): Finish Chapter 7 Start Chapter 8 on Wednesday Wednesday (2/27): Start Chapter 8 Should have read Sections 8.1-8.5 (at least) Friday (3/1): Continue Chapter 8 Should have read through Section 8.7 (at least)

Polyprotic Acids For a solution of a polyprotic acid (X M of H2A or H3A) we generally only concern ourselves with the first dissociation. Why? See Examples 7.10 and 7.11 in your text for H2SO4, and how concentration plays a role in this.

Clicker Question a) 2.90 b) 5.10 c) 7.00 d) 8.90 e) 11.10 Determine the pH of a 0.10M aqueous solution of KCN at 25°C. (for HCN Ka = 6.2 x 10–10) a) 2.90 b) 5.10 c) 7.00 d) 8.90 e) 11.10

Relating Kw to Ka and Kb  

Clicker Question How many of the following correspond(s) to a Ka expression? I. HCN (aq) + OH – (aq) CN – (aq) + H2O (l) II. HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l) III. F – (aq) + H2O (l) HF (aq) + OH – (aq) IV. HCN (aq) + H2O (l) H3O+ (aq) + CN– (aq) a) 0 b) 1 c) 2 d) 3 e) 4

Clicker Question Determine the value of K for the equation: HCN (aq) + OH– (aq) CN– (aq) + H2O (l) (for HCN Ka = 6.2 x 10–10) a) 6.2 x 10–10 b) 1.6 x 10–5 c) 6.2 x 104 d) 1.6 x 109 e) I cannot get any of these answers.

General Equation for Any Weak Acid See Example 7.17 in your text.