Chemistry Study Guide and Homework for Test #4, Spring 2013
Vocabulary:
Dilute
Concentrated
Percent Mass
Percent Volume
Molarity
Solute
Solvent
solution
Diluting a molar solution
molality
mole fraction
colligative properties
vapor pressure
Boiling point elevation
Freezing point depression
osmotic pressure
electrolyte
nonelectrolyte
dynamic equilibrium
volatile/nonvolatile
Osmosis
Semi-permeable membrane
Important concepts:
Be able to calculate molarity, percent mass/volume, molality, mole fractions, freezing point
depression and boiling point elevation. Be able to calculate how to dilute a molar solution.
Problems:
1.
Calculate the percent by mass of 3.55 g sodium chloride dissolved in 88.0 mL of water.
2.
What is the percent by volume of 25.0 mL of methanol in 75.0 mL of water?
3.
A solution is made by adding 1.23 mole potassium chloride (KCl) to 1000.0 mL of water.
What is the percent by mass of the potassium chloride solution?
4.
An 85.0 mL aqueous solution contains 7.54 g iron(II) chloride (FeCl2). Calculate the
molarity of
the solution.
5.
What is the molarity of 1.35 mole sulfuric acid (H2SO4) in a 245 mL solution?
6.
What is the molarity of 0.960 g magnesium chloride (MgCl2) in 500.0 mL of solution?
7.
What is the molarity of 9.33 g sodium sulfide (Na2S) in 450.0 mL of solution?
8.
Calculate the molality of a solution of 15.4 g sodium bromide (NaBr) dissolved in 125 g
of water.
9.
What is the molality of a solution of 15.7 g sodium chloride (NaCl) in 100.0 mL of
water?
10.
What is the molality of ions in a solution of 15.7 g sodium chloride (NaCl) in 100.0 g of
water?
11.
What is the mole fraction of calcium chloride (CaCl2) if 20.0 g calcium chloride is added
to 700.0 g of water?
12.
What is the mole fraction of water if 125.0 g magnesium hydroxide, Mg(OH)2 is
dissolved in 255 mL of water?
13.
Calculate the boiling point of 25.00 g of ethylene glycol (C2H6O2) in 50.00 g of water.
The Kbp of water is 0.512.
14.
Calculate the boiling point of 25.00 g of sodium chloride in 50.00 g of water.
15.
Calculate the boiling point of 25.00 g of magnesium chloride in 50.00 g of water.
16.
Calculate the boiling point of a solution that contains 55.40 g sodium chloride and
42.30 g potassium bromide dissolved in 750.3 mL water.
17.
Rock salt (sodium chloride), ice, and water mixture is used to cool milk and cream to
make homemade ice cream. How many grams of rock salt must be added to 1.000 kg of
water to lower the freezing point to -10.00°C? The Kfp of water is -1.86°C/m
18.
If you do not have the rock salt, and want to use sugar (sucrose) (C12H22O11) to make
your ice cream, how many grams of sucrose must be added to 1.000 kg of water to lower
the freezing point to -10.00°C?
19.
Calculate the freezing point of a solution that contains 55.40 g sodium chloride and
42.30 g potassium bromide dissolved in 750.3 mL water. (You do not have to recalculate
the molality. Use the molality you calculated in a previous problem.)
Key to problems:
1. 3.88% NaCl
2. 25.0% CH2OH
3. 8.40% KCl
4. 0.700 M FeCl2
5. 5.51 M H2SO4
6. 0.0201 M MgCl2
7. 0.265 M Na2S
8. 1.20 m NaBr
9. 2.68 m NaCl
10. 5.36 m NaCl
11. 0.00461 CaCl2
12. 0.869 H2O
13. 104.1°C
14. 108.8°C
15. 108.1°C
16. 101.8°C
17. 157 g NaCl
18. 1839 g C12H22O11
19. -6.46°C