1. 5. weak acids: the fun stuff! equilibria & Ka HA(aq)H1+(aq)+A1-(aq) or
HA(aq)+H2O(l)  H3O1+(aq)+A1-(aq) or
Chapter 15 Notes

2. questions/calculations
1. Acetic acid has Ka=1.8x10-5; hydrofluoric acid has Ka=6.8x10-4.
Which acid is stronger?
A M acetic acid sol’n has (higher/lower/same) pH as a M hydrofluoric acid sol’n.
2. Niacin is a monoprotic acid. A M aqueous solution of niacin has a pH of Calculate Ka for this compound.
Chapter 15 Notes

3. questions/calculations 3. Using Ka for niacin from question 2:
a. What is the pH of a 0.10 M niacin solution?
b. What concentration of niacin is required to lower the pH of water to 3.5?
Chapter 15 Notes

4. questions/calculations 4.
What is the % ionization of niacin in #2? in #3?
How is % ionization related to concentration for weak acids?
Chapter 15 Notes

5. Chapter 15 Notes

6. questions/calculations 5. polyprotic acids: Ka1>Ka2>Ka3 always
each equilibrium expression is valid simultaneously
Calculate the pH and the equilibrium concentrations of all species present in a M oxalic acid (H2C2O4) solution. Ka1=5.9x10-2 and Ka2=6.4x10-5
Chapter 15 Notes