Chapter 13: Solutions

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.

SuspensionSolution

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)

Practice2. 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?

Practice3. 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?