1. Ch 14/15 Test Wed up to and including 15.5

2. In Part A of your lab you created a solution that had equal moles of HA and A - and If mol HA = mol A - could we find pH? How?

3. Based on the results of your mini lab, part B… 1.What is a buffer? 2.What is it composed of? 3.Does it have any limitations?

4. Which of the following mixtures would be described as a buffer solution? 1.25.0 mL of 0.1 M NaOH and 25.0 mL of 0.1 M HCl 2.25.0 mL of 0.1 M CH 3 COOH and 25.0 mL of 0.1 M HCl 3.25.0 mL of 0.05 M NaOH and 25.0 mL of 0.1 M CH 3 COOH 4. 25.0 mL of 0.1 M NaF and 25.0 mL of 0.1 M HF

5. PROBLEM:The molecular scenes below represent samples of four HA/A - buffers. (HA is blue and green, A - is green, and other ions and water are not shown.) (a)Which buffer has the highest pH? (b)Which buffer has the greatest capacity? Why? (c)Should we add a small amount of concentrated strong acid or strong base to convert sample 1 to sample 2 (assuming no volume changes)?

6. Find the pH of 1.The original buffer: 25.0 mL of 0.1 M NaF and 25.0 mL of 0.1 M HF 2. In what range would this buffer be the most effective? 3. The solution if 10 mL of 0.10 M NaOH is added Compare to scenario if 10 mL of 0.10 M NaOH was added to 50 mL of water

7. Preparing a Buffer A buffer of pH 10.0 is needed to study the effects of acid rain on soil. Which of the following mixtures would be the best to choose? NaC 6 H 5 COO, C 6 H 5 COOH (K a of C 6 H 5 COOH = 6.3x10 -5 ) Na 2 CO 3, NaHCO 3 (K a of HCO 3 - = 4.7x10 -11 ) How many grams of Na 2 CO 3 must be added to 1.5 L of 0.20 M NaHCO 3 to make the buffer?

8. Titration Reaction of acid and base Neutralization is a one way reaction (DR) The neutralization reaction can produce an equilibrium system between a weak acid and its conjugate base (or weak base and conjugate acid)

9. Titration Curve Plot pH vs. volume of titrant added Let’s produce a titration curve for the reaction of a strong acid ( 0.10 M HCl 50 mL) with a strong base ( 0.20 M NaOH)

10. What if a weak acid was titrated against NaOH instead? 50 mL 0.10 M HC 2 H 3 O 2 (instead of HCl) titrated against strong base ( 0.20 M NaOH) What is the pH at the half equivalence point? What is the significance of this point? How would the titration curve change?

11. We need to titrate 0.25 M NH 3 with 0.15 M HCl. Which indicator would be best? IndicatorpKapH rangeColor Change Bromocresol green 4.903.8-5.4Yellow -> blue Bromothymol blue 7.306.0-7.6Yellow->blue Phenolphthalein9.508.2-10.0Colorless->Pink

12. What is this?