1. Unit 6: Solutions
Solubility

2. Solubility
Solubility: the amount of solute that dissolves in a given quantity of solvent at a given temperature to form a saturated solution
Units: grams/100 grams water

3. Saturated Solution Saturated solution:10 20 30 40 50 60 70 80 90
100 5 15 25 35 45
Temperature (oC)
g KNO3 / 100 g H2O
Solubility Curve for KNO3
Saturated solution:
Contains maximum amount of solute, will NOT dissolve any more
Any point ON the curve

4. Supersaturated Solution
More solute is dissolved than normally possible. Any point above the curve 10 20 30 40 50 60 70 80 90
100 5 15 25 35 45
Temperature (oC)
g KNO3 / 100 g H2O
Solubility Curve for KNO3

5. Unsaturated Solution Unsaturated solution:10 20 30 40 50 60 70 80 90
100 5 15 25 35 45
Temperature (oC)
g KNO3 / 100 g H2O
Solubility Curve for KNO3
Unsaturated solution:
will dissolve more solute if added
Any point below the curve

6. Example #1: What is the solubility of potassium nitrate at 40oC? 10 2030 40 50 60 70 80 90
100 5 15 25 35 45
Temperature (oC)
g KNO3 / 100 g H2O
Solubility Curve for KNO3
What is the solubility of potassium nitrate at 40oC?

7. Example #2: 10 20 30 40 50 60 70 80 90
100 5 15 25 35 45
Temperature (oC)
g KNO3 / 100 g H2O
Solubility Curve for KNO3
What is the temperature at which potassium nitrate’s solubility is 120 g/100 mL water?

8. Example #3: 10 20 30 40 50 60 70 80 90
100 5 15 25 35 45
Temperature (oC)
g KNO3 / 100 g H2O
Solubility Curve for KNO3
How many grams of potassium nitrate can be dissolved in 100 mL of water at 90oC?

9. Example #4: 10 20 30 40 50 60 70 80 90
100 5 15 25 35 45
Temperature (oC)
g KNO3 / 100 g H2O
Solubility Curve for KNO3
If you add 35 g of potassium nitrate to 100 g of water at 20oC, how much precipitate will have settled on the bottom of the dish?

11. Solubility Graph Practice!
What is the solubility of potassium nitrate at 40oC?
What is the temperature at which sodium nitrate’s solubility is 120 g/100 mL water?
How many grams of sodium nitrate can be dissolved in 100 mL of water at 90oC?
If you add 100 g of sodium chloride to 100 mL of water at 20oC, what mass of solid will have settled on the bottom of the dish?

12. g/100 g H2O
Solubility curves use concentrations in:
g solute/100 g H2O
To calculate:
mass solute (in grams) x 100g H2O
mass H2O (in grams)