Unit 11
Solutions
Chemistry Assignments and Objectives
EQ: Why does Mrs. Dempsey’s sweet tea make you cry tears of joy?
Lesson 1- Learning Targets
1. Distinguish between the terms saturated solution, unsaturated solution and supersaturated solution.
2. Identify the factors that affect solubility (temperature and pressure.)
3. Solve problems using a solubility graph.
Lesson 1 – Homework Problems
Reading a Solubility Chart
Solubility Curves of Pure Substances
How to Read the Solubility Chart:
1) The curve shows the # of grams of solute in a
saturated solution containing 100 mL or 100
g of water (density of water = 1.00 g/mL) at
a certain temperature.
150
140
KI
130
2) Any amount of solute below the line
indicates the solution is unsaturated at a
certain temperature
4) If the amount of solute is above the line but
has not all dissolved, the solution is saturated
and the # grams of solute settled on the
bottom of the container = total # g in solution
– # g of a saturated solution at that
temperature. (according to the curve)
5) Solutes whose curves move upward with
increased temperature are typically solids
because the solubility of solids increases
with increased temperature.
110
NaNO
100
grams solute per 100 grams H2O
3) Any amount of solute above the line in
which all of the solute has dissolved shows
the solution is supersaturated.
120
90
KNO3
80
70
NH4Cl
NH3
60
50
KCl
40
NaCl
30
20
KClO3
6) Solutes whose curves move downward with
increased temperature are typically gases
because the solubility of gases decreases
with increased temperature.
10
0
0
10
20
30
40
50
Temperature/Celsuis
60
70
80
90
100
Solubility Problems to solve
1. Which of the salts shown on the graph is the most soluble in water at 10oC?
2. At what temperature is 90g of Na NO3 a saturated solution in 100grams of water?
3. A solution has 70grams of KNO3 and is unsaturated, what is the minimum temperature?
4. At 20oC, a saturate solution of KClO3 is created in water. How many grams of potassium chlorate must be
added to saturate the solution at 50oC?
5. Which of the salts shown on the graph is the least soluble in water at 10oC?
6. Which of the salts shown on the graph has the greatest increase in solubility as the temperature increases
from 30 degrees to 60 degrees?
7. Which of the salts has its solubility affected the least by a change in temperature?
8. At what temperature do saturated solutions of potassium nitrate and sodium nitrate contain the same weight
of solute per 100 mL of water?
9. What two salts have the same degree of solubility at approximately 19oC?
10. How many grams of potassium chlorate must be added to 1 liter of water to produce a saturated solution at
50oC?
11. A saturated solution of potassium nitrate is prepared at 60oC using 100.mL of water. How many grams of
solute will precipitate out of solution if the temperature is suddenly cooled to 30oC?
12. Thirty grams of KCl are dissolved in 100 mL of water at 45oC. How many additional grams of KCl are
needed to make the solution saturated at 80oC?
13. What is the smallest volume of water, in mL, required to completely dissolve 39 grams of KNO3 at 10oC?
14. What is the lowest temperature at which 30. grams of KCl can be dissolved in 100 mL of water?
15. Are the following solutions saturated, unsaturated or supersaturated (assume that all three could form
supersaturated solutions)
a. 40. g of KCl in 100 mL of water at 80oC
b. 120. g of KNO3 in 100 mL of water at 60oC
c. 80. g of NaNO3 in 100 mL of water at 10oC
Lesson 2 – Learning Targets
1. Define molarity of a solution as moles of solute per liter of solution.
2. Solve problems using molarity.
3. Use M1V1 = M2V2 to calculate a new volume when diluting solutions.
Lesson 2 – Homework Problems
1. How many grams of CaCl2 would be dissolved in 1.0 L of a 0.1 M solution of CaCl2?
2. A liter of 2 M NaOH solution contains how many grams of NaOH?
3. How many grams of CaCl2 should be dissolved in 500.0 mL of water to make a 0.20 M solution of CaCl2?
4. How many grams of NaOH are in 250 mL of a 3.0 M NaOH solution ?
5. What volume of a 3.00 M KI stock solution would you use to make 0.300 L of a 1.25 M KI solution?
6. How many mL of a 5.0 M H2SO4 stock solution would you need to prepare 100.0 mL of 0.25 M H2SO4?
7. If you dilute 20.0 mL of a 3.5 M solution to make 100.0 mL of solution, what is the molarity of the new
solution?
Dilutions
8. If I have 340 mL of a 0.5 M NaBr solution, what will the concentration be if I add 560 mL more water to it?
9. If I dilute 250 mL of 0.10 M lithium acetate solution to a volume of 750 mL, what will the concentration of
this solution be?
10. If I leave 750 mL of 0.50 M sodium chloride solution uncovered on a windowsill and 150 mL of the solvent
evaporates, what will the new concentration of the sodium chloride solution be?
Unit 11 Review
1. Using the solubility graph, what substance is least soluble in hot water ? In cold water?
2. Using the solubility graph, what mass of ammonium chloride (NH4Cl) will produce a saturated solution
in 100 g of water at 50°C?
3. Using the solubility graph, what is the maximum amount of KI that can dissolve in 300 g of water at
15°C?
4. A saturated solution of KCl is made with 200 g of water at 40°C. According to the graph, how much
more KCl can be dissolved if the temperature of the solution is raised to 90°C?
5. What will usually makes a substance dissolve faster in a solvent?
6. Compare the amount of solute and solvent in a concentrated solution and also in a dilute solution.
7. How many moles of solute are in 200.0 mL of a 0.30 M solution?
8. What mass of Na2CO3 is needed to make 1.5 L of 3.5 M solution?
9. What is the molarity of a solution containing 2.5 moles of solute in 400 mL of solution?
10. What is the molarity of a solution that contains 3.0 moles of solute in 2.0 liters of solution?
11. What is the molarity of a solution containing 33 grams of solute in 540 mL of solution? (molar mass of
solute = 25 g/mol)
12. If 15.0 mL of 8.0 M HBr is used to make a 400.0 mL aqueous solution, what is the molarity of the dilute
solution?
13. To 335 mL of a 0.500 M solution of KCl, a student adds enough water to make 1.00 L of a more dilute
KCl solution. What is the molarity of the new solution?
14. What is the volume of 6.00 M HNO3 needed to make 333 mL of 2.30 M HNO3 ?