Everyone Has
Problems, but
Chemists have
Solutions
2009
Everyone has Problems, but Chemists have Solutions 2009
Section 1
1. What is a saturated solution?
Can undissolved solute remain in the bottom of a saturated solution? Explain.
2. What is an unsaturated solution?
Can undissolved solute remain in the bottom of an unsaturated solution? Explain.
3. What rule of thumb is useful for predicting whether one substance will dissolve
in another?
4. A solution is prepared by mixing 25 mL pentane (C5H12, D = 0.63 g/mL) with 45
mL hexane (C6H14, D = 0.66 g/mL). Assuming that the volumes add on mixing,
calculate the mass percent, mole fraction, molality and molarity of the pentane.
Is pentane more likely to be miscible with water or hexane? Explain.
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Everyone has Problems, but Chemists have Solutions 2009
5. You have 3.50L of solution that contains 90.0g of sodium chloride, what is the
molarity of that solution?
6. You have 0.80 L of a 0.50 M HCl solution. How many moles of HCl does this
solution contain?
7. Describe how you would prepare each of the following
 1.00L of 0.50 M solution of H2SO4 from “concentrated” (18M) sulfuric acid
 0.250 L of 0.250 M solution of HNO3 from “concentrated” (16M) nitric acid
 0.500 L of .750 M sodium carbonate from pure solid
8. To produce 40.0g of silver chromate, you will need at least 23.4g of potassium
chromate in solution as a reactant. All you have on hand in the stock room is 5L
of 6.0 M potassium chromate solution. What volume of the solution is needed
to give you 23.4g of potassium chromate needed for the reaction?
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Everyone has Problems, but Chemists have Solutions 2009
9. What is the molarity of a solution composed of 5.85g of potassium iodide
dissolved in enough water to make 0.125L of solution.
10. How many moles of H2SO4 are present in 0.500L of a 0.150 M H2SO4 solution?
11. What volume of 3.00M NaCl is needed for a reaction that requires 146.3g NaCl?
12. How many milliliters of 16.0 M HNO3 would be required to prepare 750. mL of a
0.500 M solution?
13. A solution was prepared by dissolving 17.1g of sucrose (table sugar, C12H22O11) in
125g of water. Find the molal concentration of this solution.
14. A solution of iodine, I2, in carbon tetrachloride is used when iodine is needed
for certain chemical tests. How many grams of iodine must be added to prepare
a 0.480 m solution of iodine in carbon tetrachloride if 100.0g of carbon
tetrachloride is used?
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Everyone has Problems, but Chemists have Solutions 2009
15. What is the molality of a solution composed of 255g acetone, (CH3)2CO,
dissolved in 200.g of water?
16. What quantity, in grams, of methanol, CH3OH, is required to prepare a 0.244 m
solution in 400.g of water?
17. How many grams of AgNO3 are needed to prepare a 0.125 m solution in 250. mL
of water?
Section 2
1. Use the graph on slide 18 to explain how the solubility of the following
substances is affected by temperature.
 potassium dichromate

cesium sulfate

lead (II) nitrate

sodium chloride
2. Determine the solubility of sodium nitrate at 10 oC.
3. Determine the solubility of potassium chloride at 50 oC.
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Everyone has Problems, but Chemists have Solutions 2009
4. At what temperature would the solubility of potassium chlorate be 20g per
100g of H2O?
5. If 30g of KClO3 was added to 100g of H2O at 10oC, would the resulting solution
be saturated or unsaturated? Explain.
6. What would happen if 30g of KClO3 was added to 100g of H2O at 35 oC?
Section 3
1. How does pressure affect the solubility of a gas in a liquid?
2. Which law is a statement of this relationship? (State the name of the law, list
the formula, and identify each of the variables)
3.
Two bottles of soda are opened. One is a cold bottle and the other is partially
frozen. Which system will show more effervescence and why?
4. The solubility of CO2 in water at 25 oC and 1 atm is 0.034 mol/L. What is the
solubility under atmospheric conditions? (The partial pressure of CO2 in air is
0.0003 atm.) Assume that CO2 obeys Henry’s Law.
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Everyone has Problems, but Chemists have Solutions 2009
Section 4
1. Identify the following compounds as being electrolytes or nonelectrolytes
 C6H12O6 (glucose)

Sodium phosphate

Ethylene glycol

Barium chloride
2. What determined the strength with which a solute acts as an electrolyte?
3. Distinguish between the use of the terms strong and weak and the use of the
terms dilute and concentrated when used to describe electrolyte solutions.
4. A solution is prepared by dissolving 396 g of sucrose (C12H22O11) in 624 g of
water. What is the vapor pressure of this solution at 30 oC? (Use your
reference sheet to determine the vapor pressure of water at 30 oC.)
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Everyone has Problems, but Chemists have Solutions 2009
5. How many grams of sucrose, C12H22O11, must be added to 552 g of water to give a
solution with a vapor pressure 2.0 mm Hg less than that of pure water at 20 oC?
Section 5
1. How does the presence of a nonvolatile solute affect each of the following
properties of the solvent into which the solute is dissolved?
 vapor pressure

freezing point

boiling point
2. Compare the effects of nonvolatile electrolytes with the effects of nonvolatile
non-electrolytes on the freezing and boiling points of solvents in which they are
dissolved, and explain why such differences are observed.
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Everyone has Problems, but Chemists have Solutions 2009
3. Write the equation for the dissolution of each of the following ionic compounds
in water.
 potassium iodide
 sodium nitrate
 magnesium chloride
 sodium sulfate
4. For the compounds listed in the previous problem, determine the number of
moles of each ion produced as well as the total number of moles of ions
produced when 1 mol of each compound dissolves in water.
 potassium iodide
 sodium nitrate
 magnesium chloride
 sodium sulfate
5. Calculate the concentration of all ions present in each of the following solutions
of strong electrolytes.

0.15 M Al(NO3)3

0.25 M K2Cr2O7
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Everyone has Problems, but Chemists have Solutions 2009
6. Determine the freezing-point depression of H2O in each of the following solutions.

1.50m solution of C12H22O11 (sucrose) in water.

171g of C12H22O11 in 1.00 kg ethanol

77.0 g of C12H22O11 in 400. mL of water
7. Determine the molality of each solution of an unknown non-electrolyte in water,
given the following freezing-points.
 –0.930 oC

–3.72 oC
8. Determine the molality of a solution containing an unknown non-electrolyte
dissolved in benzene, given that the solution’s freezing point is -1.37 oC.
9. A solution contains 20.0g of C6H12O6 (glucose) in 250.g of water.
 What is the freezing-point depression of the solvent?

What is the freezing point of the solution?
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Everyone has Problems, but Chemists have Solutions 2009
10. How many grams of antifreeze, C2H4(OH)2, would be required per 500.g of water
to prevent the water from freezing until it reached a temperature of –20.0 oC?
11. If 1.500g of a solute having a molar mass of 125.0g were dissolved in 35.00g of
cyclohexane, what would be the resulting freezing point of the solution?
12. Determine the boiling-point elevation of water in each of the following solutions.
 2.5m solution of C6H12O6 (glucose) in water

32.0g C6H12O6 in 1.00 kg water

50.0g C6H12O6 in 500. mL of water
13. Determine the molality of each solution of an unknown non-electrolyte in water,
given the following boiling-points.

100.25 oC

101.53 oC
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Everyone has Problems, but Chemists have Solutions 2009
14. Determine the molality of a solution containing an unknown non-electrolyte
dissolved in benzene, given that the solution’s boiling point is 92.4 oC.
15. Given 1.00m aqueous solutions of each of the following electrolytic substances,
what is the expected change in the freezing point of the solvent?
 potassium iodide

calcium chloride

barium nitrate
16. What is the expected change in the freezing point of water for an aqueous
solution that is 0.015m aluminum chloride?
17. What is the expected freezing point of a solution containing 85.0g of sodium
chloride dissolved in 450. mL of water?
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Everyone has Problems, but Chemists have Solutions 2009
18. Calculate the expected freezing point of a solution containing 1.00 kg of ethanol
and 0.250 mol of NaCl.
19. Given 0.01m aqueous solutions of each of the following, rank the solutions in
order of increasing change in the freezing point of the solution (1 would have
the freezing point closest to water). Explain your answer.
a. _____ sodium iodide
b. _____ calcium chloride
c. _____ potassium phosphate
d. _____ glucose (C6H12O6)
20. What is the molal concentration of an aqueous calcium chloride solution that
freezes at –2.43 oC?
21. If a red blood cell was placed in a hypotonic solution, would you expect the rbc
to swell, remain the same, or burst? Explain.
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Everyone has Problems, but Chemists have Solutions 2009
22. Pheromones are compounds secreted by the females of many insect species to
attract males. One of these compounds contains 80.78 percent C, 13.56
percent H, and 5.66 percent O. A solution of 1.00 g of this pheromone in 8.50 g
of benzene freezes at 3.37 oC. What are the molecular formula and molar mass
of this compound? (Always assume an unknown compound is a nonelectrolyte,
unless otherwise stated.)
23. A solution of 2.50 g of a compound having the empirical formula C6H5P in 25.0 g
of benzene is observed to freeze at 4.3 oC. Calculate the molar mass of the
solute and its molecular formula.
Section 6
1. What is the Tyndall effect?
Identify one example of this effect.
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