Schedule Today (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)

Acid-Base Question Consider the weak acid HA with Ka = 1.00 x 10–6. 1. Determine the pH of a solution that is 1.00M HA(aq). 2. Determine the pH of a 1.0-L solution to which you add 2.00 moles of HA and 1.00 mole of NaOH. 3. Determine the pH of a 1.0-L solution to which you add 1.00 mole of HA and 1.00 mole of NaOH.

General Equation for A Buffered Soln. If [HA]0 and [A–]0 are high enough, no need for this! If [A–]0 = 0, this becomes the equation we saw in Chapter 7.

General Equation for A Buffered Soln. rxn: HA + OH– or A– + H3O+ MS: HA, A–, H2O K = “very large” K = Ka or Kb

Slowly adding a base to a weak acid… Start with 1.00-L of 1.00M HA (Ka = 1.00 x 10–6) Added NaOH pH change in pH (see earlier work) 3.00 -- 0.05 4.72 1.72 0.10 5.05 0.33 0.15 5.25 0.20 5.40 0.25 5.52 0.12 0.30 5.63 0.11

Slowly adding a base to a weak acid… Start with 1.00-L of 1.00M HA (Ka = 1.00 x 10–6) Added NaOH pH change in pH 0.35 5.73 0.10 0.40 5.82 0.09 0.45 5.91 0.50 6.00 0.55 6.09 0.60 6.18 0.65 6.27

Slowly adding a base to a weak acid… Start with 1.00-L of 1.00M HA (Ka = 1.00 x 10–6) Added NaOH pH change in pH 0.70 6.37 0.10 0.75 6.47 0.80 6.60 0.13 0.85 6.75 0.15 0.90 6.95 0.20 095 7.27 0.32 1.00 (see earlier work) 10.00 2.73

Slowly adding a base to a weak acid… Initial jump in pH, buffer region, jump at equivalence