Chapter 13: Solutions
13.1: What is a Solution?
• Objectives:
(1) Distinguish between solutions, suspensions,
and colloids.
(2) Describe some techniques that chemists use
to separate mixtures.
Solution
Suspension
Colloid
Recall…
• Homogeneous mixture: A mixture has a
uniform composition.
• Heterogeneous mixture: A mixture that does
not have a uniform composition.
Solution
• Solution: A homogeneous mixture.
• Parts of a solution:
– Solute: The substance that is dissolved in the solvent.
– Solvent: The substance in which the solute is dissolved.
• Examples: Salt dissolves in water.
– Salt is the solute.
– Water is the solvent.
• Any solution in which water is the solvent is called an aqueous
solution.
Practice
• Identify the solute and solvent in each of the
following solutions:
1. Sugar is dissolved in tea.
2. Calcium chloride is dissolved in water.
Suspension
• Suspension:
– Temporary heterogeneous mixture
– The different parts of the mixture spontaneously
separate over time
• Examples:
– Clay in water (clay settles to the bottom over time)
– Sand in water (sand settles to the bottom over time)
Colloid
• Colloid:
– Stable heterogeneous mixture
– Particles dispersed evenly but not dissolved
– Particles suspended but do not settle
– Scatter light
• Examples:
– milk, gelatin desserts, whipped cream,
mayonnaise, fog
Summary
•
•
•
•
•
•
What is a solution?
What is the solute?
What is the solvent?
What is a suspension?
What is a colloid?
What are 6 methods for separating mixtures?
13.2 Molarity
• Objective:
(1) To calculate the concentration of a solution
in terms of molarity.
Concentration
• Concentration: amount of solute in solution
• Can be measured in many different ways:
– Molarity
– Molality
– Percent composition
– Parts per million (ppm)
Molarity
• Molarity = moles of solute
liters of solution
• Example: 0.30 mol KBr are present in 0.40 L of
solution.
• [KBr] = 0.30 mol = 0.75 M KBr
0.40 L
Practice: Calculating Molarity
1. Calculate the molarity of a solution with 0.38
mol of copper (II) sulfate dissolved in 0.50
liters of solution.
Practice: Calculating Molarity
Unfortunately, it doesn’t stay that easy…
2. What is the molarity of potassium chloride
solution that has a volume of 400.0 mL and
contains 85.0 g KCl?
Practice: Calculating Molarity
3. Vinegar contains 5.0 g of acetic acid,
CH3COOH, in 100.0 mL of solution. Calculate
the molarity of acetic acid in vinegar.
4. If 18.25 g HCl is dissolved in enough water to
make 500.0 mL of solution, what is the
molarity of the HCl in solution?
Practice: Calculating Molarity
5. If 20.0 g H2SO4 is dissolved in enough water to
make 250.0 mL of solution, what is the molarity
of the sulfuric acid solution?
6. A solution of silver nitrate contains 29.66 g of
solute in 100.0 mL of solution. What is the
molarity of the solution?
7. A solution of barium hydroxide contains 4.285 g
of barium hydroxide in 100.0 mL of solution.
What is the molarity of the solution?
Practice: Solving for mass
8. What mass of KBr is present in 25 mL of 0.85
M solution of KBr?
9. What mass of NaCl is present in 430.0 mL of a
0.45 M NaCl solution?
Stoichiometry and Molarity
1. An excess of zinc is added to 125 mL of 0.100 M
HCl solution. What is the mass of zinc chloride
formed? (hyrogen gas is also a product)
Practice
2. Commercial hydrochloric acid, HCl, is 12.0 M. Calculate
the mass of HCl in 250.0 mL of the solution.
3. What volume (in mL) of a 0.500 M solution of copper
(II) sulfate is needed to react with an excess of
aluminum to provide 11.0 g of copper?
4. Yellow CdS is prepared by reacting ammonium sulfide
with cadmium nitrate. What mass of CdS can be
prepared to mixing 2.50 L of 1.25 M cadmium nitrate
solution with an excess of ammonium sulfide?
13.3 Dilutions
• Objective:
(1) To calculate the molarity of a diluted
solution.
13.3 Dilutions
• The sulfuric acid we buy comes in 18M.
• I need 4 M for my lab.
• What should I do?
13.3 Dilutions
• The sulfuric acid we buy comes in 18M.
• I need 4 M for my lab.
• What should I do?
DILUTE IT!!
Dilutions
M1V1 = M2V2
I have 18.0 M sulfuric acid. I need 3.0 L of 4.0 M
sulfuric acid. What volume of concentrated
sulfuric acid should I use?
Practice
1. What is the molarity of a solution that is
made by diluting 50.00 mL of a 4.74 M
solution of HCl to 250.0 mL?
Practice
2. What volume should 1.19 mL of an 8.00 M
acetic acid solution be diluted in order to
obtain a final solution that is 1.50 M?
Practice
3. What is the molarity of a solution of ammonium
chloride prepared by diluting 50.0 mL of a 3.70 M
ammonium chloride solution to 2.00 L?
4. What volume of water would be added to 16.5
mL of a 0.0813 M solution of sodium borate in
order to get a 0.0200 M solution?
5. What volume of water would you add to 15.0 mL
of a 6.77 M solution of nitric acid in order to get a
1.50 M solutions?
13.4 Solubility Curves
• Objective:
(1) To define saturated solution, unsaturated
solution, and supersaturated solution.
(2) To read a solubility curve.
(3) To analyze a solubility curve
Solubility Curve
• Solubility Curve: tells us how much solute can
be dissolved at a given temperature.
Saturation
• Saturated Solution: A solution that cannot
dissolve any more solute under the given
conditions.
• Unsaturated Solution: A solution that contains
less solute than a saturated solution and that is
able to dissolve additional solute.
• Supersaturated Solution: A solution holding more
dissolved solute than what is required to reach
equilibrium at a given temperature.
Solubility Curve
Practice
1.) How many grams of
NH4Cl must dissolve
for NH4Cl to be
saturated at 90⁰C?
Practice
2.) How many grams of
NH4Cl must dissolve
in 500 g of H2O to be
saturated at 90⁰C?
Practice
3.)Which solute’s
solubility changes the
most with temperature?
4.) Which changes the
least?
5.) Which solute (s) do not
follow the “trend”?
Practice
6.) How many grams of
sodium nitrate will
dissolve in 300 g of
water 20⁰C?
Practice
7.) 500 g of water is
used to make a
saturated solution of
KCl at 10⁰C. How
many more grams of
KCl could be
dissolved if the
temperature was
raised to 100⁰C?
Practice
8.) A saturated solution
of potassium nitrate
in 200g of water at
50⁰C is cooled to
20⁰C. How much
potassium nitrate will
precipitate out of the
solution?