1. Take out your homework

2. The pH of a 0.150 M solution of a weak acid is 4.10. Calculate the Ka value of the acid.

3.  Saturday School: 10-11ish  Monday: Cold Call Quiz

5. How do we know when to use an ICE table to determine pH? Consider the following two problems 1. Determine the pH of a solution of 0.050 M HCl 2. Determine the pH of a solution of 0.080 M HF

6. Give each group a different problem Consider a solution of Weak Acid HA  H + + A - 1. Determine the pH of the solution if [HA] = ? M 2. What species is present in the greatest concentration? 3. On your whiteboard, model the relative concentrations of each species HNO2 Ka = 4.0 x 10 -4 HCOOH Ka = 1.77 x 10 -4 HF Ka = 7.2 x 10 -4

7. What can we conclude about the relative concentrations of each species of a weak acid at equilibrium? What is present in greatest quantity? What is present in the lowest quantity?

8. Consider the following two solutions HNO 2 : pH = 3.5 HCl: pH = 3.5 Which solution has the greater concentration of hydronium ion in solution?

9. Kw = Ka * Kb

10. Calculate the K a for the ammonium ion (K b = 1.8 x 10 -5 )

11. Consider the following two acids and their ionization constants: HCOOHKa = 1.7 x 10 -4 HCNKa = 4.9 x 10 -10 Which conjugate base (HCOO- or CN-) is stronger? Explain.

12. Polyprotic acids: Acid that can donate more than one H+ Calculations of Ka are more complicated because you need to take into account all potential ionizations We’ll focus just on monoprotic acids Acid Strength based on structure Increasing size and EN leads to an increase in acid strength Essentially, if molecule can ionize easier, it is a stronger acid Increasing size and EN weakens bond