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Chapter 12 Problem Set Key: Preparing Laboratory Solutions that
Contain One Solute
PART A: Percent solutions
1. How much ethanol is present in 200 mL of a 25% (v/v) solution of
ethanol?
50 mL ethanol
2. A laboratory solution contains water and ethylene glycol. How could
you prepare 150 mL of a 40% (v/v) solution of ethylene glycol?
Measure 60 mL ethylene glycol and add enough water to make 150 mL
total solution
3. A laboratory solution is 15% (v/v) acetonitrile, 35% (v/v) methanol in
water. How could you prepare 100 mL of this solution?
Measure 15 mL acetonitrile, 35 mL methanol and bring to a total volume
of 100 mL with water.
4. A particular laboratory solution contains 5 L of propanol per 10 mL of
solution. Express this as a percent (v/v) propanol solution.
0.05% propanol
5. A solution contains 15 mL of ethanol per 1 L total volume. Express this
as a percent (v/v) ethanol solution.
1.5% ethanol
6. A solution contains 158 mL of acetone per liter of solution. Express this
as a percent (v/v) acetone solution.
15.8% acetone
PART B: Parts per million and parts per billion
1. Convert: 1 mg/L = 1 ppm
2. Convert: 1 g/L = 0.001 ppm
3. Convert: 1 ppm = 1g/mL
4. Convert: 35 mg/mL = 35,000 ppm
5. Convert: 432 ppm = 0.432 g/L
6. Convert: 17 g/L = 17,000 ppm
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PART C: Molarity
1. If the concentration of a solute in a solution is 2.00 X 10-3 moles/liter,
how many moles are there in 500 mL of this solution?
0.001 moles
2. If a solute has a concentration of 0.1 moles/L, how much solute is present
in 10 mL of solution?
0.001 moles
3. You add 29.2 g of NaCl to a total volume of 1L. Express the final
concentration of this solution in terms of molarity. (FW of NaCl =
58.44)
0.5 M
4. You add 12.0 g of NaCl to a total volume of 1L. Express the final
concentration of this solution in terms of molarity. (FW of NaCl =
58.44)
0.21 M
5. You add 58.4 g of NaCl to a total volume of 500 mL. Express the final
concentration of this solution in terms of molarity. (FW of NaCl =
58.44)
2M
6. You add 40.0 g of NaCl to a total volume of 500 mL. Express the final
concentration of this solution in terms of molarity. (FW of NaCl =
58.44)
1.37 M
7. How much KCl is present in 250 mL of a 100 mM solution? (FW of KCl
= 74.55)
1.86 grams KCl
8. How much CaCl2 is required to make up 150 mL of 800 M CaCl2?
(FW of CaCl2 = 111.0)
0.013 g CaCl2
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PART D: Weight/volume solutions
1. Enzymes are proteins that catalyze chemical reactions in biological
systems. Enzymes are rated on the basis of how active they are, or how
quickly they can catalyze reactions. Every preparation of enzyme has a
certain activity expressed in units of activity.
 Suppose you buy a vial of an enzyme called -galactosidase. The
vial is labeled:
100 mg solid; 5000 Units/mg
How many units are present in the vial?
500,000 units
2. A vial of the enzyme horseradish peroxidase is labeled:
250 mg solid; 200 Units/mg
How many units are present in this vial?
50,000 units