1. Review Practice
What is the molality of a solution created by adding 58 grams of magnesium hydroxide to 4 liters of water?
Answer: m Mg(OH)2
What is the molality of a solution created by adding 49 grams of sulfuric acid to 3 liters of water?
Answer: m H2SO4

2. Calculating Ion Concentration
Write the dissociation equation.
Determine the concentration of the solution.
Use dimensional analysis and stoichiometry to determine ion concentration.
Example:
What is the hydrogen ion concentration if 2 moles of sulfuric acid are dissolved in 6 liters of solution?
H2SO4 → 2H+ + SO42-
2 moles H2SO4
2 moles H+
= 0.67 M [H+]
6 L sol’n
1 moles H2SO4

3. Now you try
What is the hydrogen ion concentration of a 3 liter solution with 24.5 grams of phosphoric acid?
0.25 M [H+]
What is the hydroxide ion concentration of a 5 liter solution with 7.4 grams of calcium hydroxide?
0.04 M [OH-]

4. You try
What is the hydrogen ion concentration of a 0.2 molar phosphoric acid solution?
Answer: 0.6 M [H+]
What is the hydroxide ion concentration of a solution made by adding 34 grams of calcium hydroxide to enough water to make 2 liters of solution?
0.5 M [OH-]

5. Acids and Bases Acids produce hydrogen ions when dissolved in water.
HCl → H+ + Cl-
Have a pH less than 7.
Bases produce hydroxide ions when dissolved in water.
Ca(OH)2 → Ca2+ + 2OH-
Have a pH greater than 7
Pure water is neutral with a pH of 7

6. pH scale
Scale used to show hydrogen ion concentration [H+] in a solution.
pH scale ranges from 0-14.
pH < 7 acidic
pH > 7 basic
pH = 7 neutral
pH = -log [H+]

7. You Try Calculate the pH of the following hydrogen ion concentrations.
0.01 M [H+]
0.006 M [H+]
0.4 M [H+]
M [H+]

8. More
Calculate the pH of a 250 mL solution with 7.3 grams of hydrochloric acid.
pH = 0.10
Calculate the pH of a 475 mL solution with 19.6 grams of sulfuric acid solution.
pH = 0.075
Calculate the pH of a 1.6 Liter solution with 49 grams of phosphoric acid.
pH = 0.028

9. pOH scale
Scale used to show hydroxide ion concentration [OH-] in a solution.
pOH scale ranges from 0-14.
pOH > 7 acidic
pOH < 7 basic
pOH = 7 neutral
pOH = -log [OH-]
pH + pOH = 14
[OH-] = 10-pOH
[H+] x [OH-] = 1 x 10-14

10. Practice
What is the pOH of a 5 Liter solution with 148 grams calcium hydroxide solution?
pOH = 0.10 basic
What is the pOH of a 375 mL solution with grams of aluminum hydroxide? Is this solution acidic or basic?
pOH = 2.50 basic
What is the pH of a 50 mL solution with grams of magnesium hydroxide? Is this solution acidic or basic?
pH = 10.9 basic