Practice Problems
Solutions
State Standards 6 a and 6 d
1. Define the following terms
A. Solution
a homogeneous mixture involving two or more pure substances.
B. Solute
substance dissolved in the solution.
C. Solvent
the substance in which the solute is dissolved
Molarity
2.
What is the molarity of HCl when 15.89 g of HCl (g) is added to water yielding a total combined
volume of 1.900L?
15.89g x 1 mole HCl = 0.4359 moles
36.45g
0.4359 moles
1.900 L
3.
x
1 mole K2SO4
174.27g
0.2599 moles
1.2001 L
=
= 0.2599 moles
0.217 M
What is the molarity when 315g of HNO3 is dissolved in 6 liters of water?
315g
x
1 mole HNO3
63g
5 moles HNO3
6L
5.
0.2294 M
What is the molarity of a solution made by dissolving 45.3 g of K2SO4 (molar mass 174.27 g) in
1.2001 L of solution?
45.3g
4.
=
=
= 5 moles
0.833 M
A 10.00 ml sample of blood contains 45.8 mg of sodium ions. What is the molarity of the sodium ion
in the blood sample? (First covert from ml to liters and from mg to grams)
45.8mg x
1g
=
1000mg
0.0458g
x
1 mole Na
23g
=
0.001991 moles
10.00mL
x
1L
1000mL
=
0.0100L
0.001991 moles =
0.0100L
0.0458g
0.1991M
6.
What is the molarity of a solution prepared containing 5.6 g of sodium perchlorate (NaClO4) in 0.50 L?
5.6g
x
1 mole NaClO4
122.45g
0.0457 moles
0.5 L
7.
=
x
1 mole = 0.00048 moles
208.2g
0.00048 moles
0.080 L
=
0.0060 M
What is the molarity of a solution prepared containing 1.55 L containing 153 g of sodium carbonate
NaCO3?
153g
x
1 mole = 1.84 moles
83g
1.84 moles
1.55 L
9.
0.091 M
What is the molarity of a solution prepared containing 0.10 g of barium chloride BaCl2 in 0.080L?
0.10g
8.
= 0.0457 mole
=
1.19 M
What is the molarity of a solution prepared containing 0.10 L containing 2.3 g of potassium nitrate
KNO3?
2.3g
x
1 mole = 0.02275 moles
101.1g
0.02275 moles
0.10 L
=
0.2275 M
Determine the number of grams needed to make the following solutions.
10. How many grams of AgNO3 must be added to make 0.10 L of 0.10 M silver nitrate solution?
0.10L
x
0.01 moles
0.10 mole
L
x
= 0.01 moles
169.9g =
mole
1.699g
11. How many grams of NaCN must be added to make 5.0 mL of 0.05 M sodium cyanide solution?
5mL
x
0.005L x
1L
1000mL
= 0.005L
0.05mole
L
=
0.00025 mole
0.00025 mole
x
49g
1 mole
=
0.01225g
12. How many grams of KCl must be added to make 0.125 L of 0.10 M potassium chloride solution?
0.125mL
x
1.0 mole
L
0.125 mole x
= 0.125 mole
74.55g =
mole
9.32g
13. How many grams of KMnO4 must be added to make 250 mL of 0.0014 M potassium permanganate
solution?
250mL x
1L
1000mL
= 0.250L
0.250L x
0.0014 =
L
0.00035 moles
x 158.04g
mole
0.00035 moles
=
0.0553g
14. How many grams of sodium carbonate are required to make 2.0 L of a 1.5 M sodium carbonate
NaCO3?
2.0L
3 moles
x
1.5 moles
L
x
83g =
mole
= 3 moles
249g
Dilutions M1V1 = M2V2
15. To what volume, in liters, must you dilute a solution containing 3 liters of 0.100 M of Ca(OH)2 to
obtain a 0.00100 M solution as calcium hydroxide (Ca(OH)2)?
(0.100M)(3L)
V2 =
=
(0.00100M)(V2)
300L
16. 55.4 mL of 0.210 M sulfuric acid is diluted to 1.00 L. What is the new molarity?
(0.210M)(55.4mL)
M2 =
=
M2 (1.00L)
11.6
17. What final volume in liters must you dilute 50.0 mL of 0.100 M CuSO4 to obtain a 0.0025 a molarity
solution as copper sulfate?
(0.100M)(50.0mL)
=
(0.0025M)(V2)
V2 =
2000mL
18. Calculate the boiling point of a 3.0 m aqueous (water) sugar solution (C12H22O11)?. Use the data
presented in the table below.
(3.0M)(0.51°C) = 1.53°C
m
100°C + 1.53°C
=
101.53°C
Molal Boiling Point Elevation and Freezing Point Depression
Solvent
BP (°C)
Kb (°Cm-1)
MP (°C)
Kf (°Cm-1)
water
100
0.51
0
1.86
Cyclohexane 80.7
2.69
6.5
20.0
Acetic Acid 118.3
3.07
16.6
3.57
19. Gold is perhaps the first pure metal known to man and is present to the extent of .85 mg of gold for
every 200 L of the earth’s crust, on the average. Calculate the ppm of gold in the earth’s crust.
.85mg
200L
=
0.00425
20. Calculate the percent concentration (mass/mass) of a solution that is made by dissolving 35 g KMnO4
in 350 g of water.
35 g
385 g
x
100 =
9.09%