Solubility Curve Practice Problems Worksheet 1

Intro questions:

You'll notice that for most substances, solubility increases as temperature increases. As discussed earlier in solutions involving liquids and solids typically more solute can be dissolved at higher temperatures. Can you find any exceptions on the graph?______

Here's an example of how to read the graph. Find the curve for KClO3.

At 30°C approximately 10g of KClO3 will dissolve in 100g of water. If the temperature is increased to 80°C, approximately ______of the substance will dissolve in 100g (or 100mL) of water.

Directions: Use the graph to answer the following questions. REMEMBER UNITS!

1)What mass of solute will dissolve in 100mL of water at the following temperatures?

  1. KNO3 at 70°C = ______
  2. NaCl at 100°C= ______
  3. NH4Cl at 90°C= ______
  4. Which of the above three substances is most soluble in water at 15°C. = ______

2)Types of Solutions

On a solubility curve, the lines indicate the concentration of a ______solution - the maximum amount of solute that will dissolve at that specific temperature.

Values on the graph ______a curve represent unsaturated solutions - more solute could be dissolved at that temperature.

Label the following solutions as saturated or unsaturated. If unsaturated, write how much more solute can be dissolved in the solution.

Solution / Saturated or Unsaturated? / If unsaturated: How much more solute can dissolve in the solution?
a solution that contains 70g of NaNO3 at 30°C (in 100 mL H2O)
a solution that contains 50g of NH4Cl at 50°C (in 100 mL H2O)
a solution that contains 20g of KClO3 at 50°C (in 100 mL H2O)
a solution that contains 70g of KI at 0°C (in 100 mL H2O)

1. a. What is the solubility of KClat 5C? ______

b. What is the solubility of KClat 25C? ______

c. What is the solubility of Ce2(SO4)3 at 10C? ______

d. What is the solubility of Ce2(SO4)3 at 50C? ______

2. a. At 90C, you dissolved 10 g of KCl in 100. g of water. Is this solution saturated or unsaturated?

b. How do you know?

3. A mass of 100 g of NaNO3 is dissolved in 100 g of water at 80ºC.

a) Is the solution saturated or unsaturated?______

b) As the solution is cooled, at what temperature should solid first appear in the solution? Explain.

4. Use the graph to answer the following two questions:

Which compound is most soluble at 20 ºC? ______

Which is the least soluble at 40 ºC? ______

5. Which substance on the graph is least soluble at 10C? ______

6. A mass of 80 g of KNO3 is dissolved in 100 g of water at 50 ºC. The solution is heated to 70ºC. How many more grams of potassium nitrate must be added to make the solution saturated? Explain your reasoning (See question #2 on the other side for a hint)

Challenging questions:

  1. What would happen if a saturated solution of potassium chloride, KCl, in 100g of water was cooled from 80°C to 40°C?
  1. When 50 grams of potassium chloride, KCl, is dissolved in 100 grams of water at 50 ºC, the solution can be correctly described as:
  1. What mass of potassium chlorate, KClO3 could be dissolved in 100mL of water at 70°C?
  1. A beaker containing 80 grams of lead(II) nitrate, Pb(NO3)2, in 100 grams of water has a temperature of 30 ºC. Approximately how many grams of the salt are undissolved, on the bottom of the beaker?
  1. A solution of potassium chlorate, KClO3, has 20 grams of the salt dissolved in 100 grams of water at 70 ºC. Approximately how many more grams of the salt can be added to the solution before reaching the saturation point?
  1. When 30 grams of potassium nitrate, KNO3, is dissolved in 100 grams of water at 20 ºC, the solution can be correctly described as:
  1. How many grams of sodium nitrate, NaNO3, are soluble in 100 g of water at 10 ºC?
  1. When 20 grams of potassium chlorate, KClO3, is dissolved in 100 grams of water at 80 ºC, the solution can be correctly described as:

9. What mass of lead (II) nitrate will dissolve to make a saturated solution in 25.0 ml of water at 20C?

10.What mass of sodium chlorate dissolves 33.3ml of water at 40C to make a saturated solution?

11. What mass of lithium sulfate dissolves in 20.0 ml of water at 35C to make a saturated solution?

12. What mass of potassium chromate precipiatates from solution if a saturated solution in 60.0g of water is cooled from 82C to 40C?

13. What mass of potassium chloride precipitates from a saturated solution in 15g of water when it is cooled from 90C to 30C?

14. A 200.0ml saturated solution of potassium nitrate is made at 90C. If 15% of the solvent evaporates as the solution is slowly cooled to 30C, what mass of precipitate is produced?