1. Unit 8 Solution Chemistry
Chapters 12 & 13

2. Chapter 12
SOLUTIONS

3. Chapter 12 – Section 1: Types of Mixtures
A mixture is two or more substances which are mixed together but not chemically combined.
Mixtures can be solid, liquid or gas.

4. Heterogeneous Mixtures
Chapter 12 – Section 1: Types of Mixtures
Heterogeneous Mixtures
A heterogeneous mixture consists of visibly different substances.

5. Chapter 12 – Section 1: Types of Mixtures
Homogeneous Mixtures
A homogeneous mixture has the same uniform appearance and composition.

6. Chapter 12 – Section 1: Types of Mixtures
Solutions
A solution is a homogeneous mixture of two or more substances in a single phase.
Solvent – the dissolving medium.
Solute – the substance being dissolved.
Solutions may exist as gases, liquids, or solids.
Alloys – solid solutions in which the atoms of two or more metals are uniformly mixed (i.e. brass, 14 K gold.)

7. Chapter 12 – Section 1: Types of Mixtures
Suspensions
A suspension is a mixture in which the particles are so large that they settle out unless the mixture is constantly stirred or agitated.
Particles in a suspension are over 1000 nm in diameter—1000 times as large as atoms.

8. Chapter 12 – Section 1: Types of Mixtures
Colloids
A colloid is a mixture in which the particles are intermediate in size between those in solutions and suspensions.
Many colloids look like solutions because their particles cannot be seen.
But colloids exhibit the Tyndall effect – the scattering of light by colloidal particles. (example: a headlight beam on a foggy night.)

9. Solutions, Colloids, and Suspensions
Chapter 12 – Section 1: Types of Mixtures
Solutions, Colloids, and Suspensions
The table below shows a comparison between the properties of solutions, colloids and suspensions (from pg in your book.)

10. Chapter 12 – Section 1: Types of Mixtures
Electrolytes
Electrolyte – a substance that conducts electricity when it is dissolved in water.

11. Dissolving a Solid in a Liquid
Chapter 12 – Section 2: The Solution Process
Dissolving a Solid in a Liquid
The following 3 factors affect the rate at which a solid dissolves in a liquid :
Surface area – a solute dissolves faster if surface area is increased.
Agitating a solution – shaking or stirring makes dissolving faster.
Increased temperature – most substances dissolve faster in hot water.
Visual Concept

12. Saturated, Unsaturated, and Supersaturated Solutions
Chapter 12 – Section 2: The Solution Process
Saturated, Unsaturated, and Supersaturated Solutions
A saturated solution contains the maximum amount of dissolved solute.
A solution that contains less than the maximum amount of solute is unsaturated.
A supersaturated solution contains more than the maximum amount of solute that can be dissolved under existing conditions.

13. Chapter 12 – Section 2: The Solution Process
Solubility
Solubility – the amount of a substance that will dissolve in a specific amount of solvent at a certain temperature. (example: The solubility of sugar is 204 g per 100 g of water at 20°C.)
Solubility varies greatly between different types of compounds.

14. Solute-Solvent Interactions
Chapter 12 – Section 2: The Solution Process
Solute-Solvent Interactions
“Like dissolves like”
Polar solvents will dissolve polar solutes.
Non-polar solvents will dissolve non-polar solutes.
Liquids that dissolve in one another are miscible. Liquids that don’t dissolve each other are immiscible.
Miscible
Immiscible

15. Chapter 12 – Section 2: The Solution Process
Solubility of a Gas
There are 2 main factors that affect the solubility of a gas in a liquid:
Temperature – decreasing the temperature generally increases the solubility of a gas.
Pressure – Increasing the pressure increases the solubility of a gas.
Effervescence – The rapid escape of a gas from a liquid due to a decrease in pressure.
Visual Concept

16. Properties of Solutions
Chapter 12 – Section 2: The Solution Process
Properties of Solutions
Solution equilibrium – state in which the opposing processes of dissolution and crystallization occur at the same rates.
Enthalpy of solution – the amount of energy absorbed as heat by the solution when a specific amount of solute dissolves in a solvent. A negative enthalpy of solution means that energy is released.

17. Chapter 12 – Section 3: Concentration of Solutions
The concentration of a solution is a ratio of solute to solvent.
Concentrated means that there is a relatively large amount of solute in a solvent.
Dilute means that there is a relatively small amount of solute in a solvent.

18. Chapter 12 – Section 3: Concentration of Solutions
Molarity
Molarity is the number of moles of solute in one liter of solution.
The symbol for molarity is M.
moles of solute
Molarity (M) =
liters of solution
Visual Concept

19. Molarity Calculations Sample Problem A
Chapter 12 – Section 3: Concentration of Solutions
Molarity Calculations Sample Problem A
You have 3.50 L of solution that contains 90.0 g of NaCl. What is the molarity of that solution?
Solution:
First, you need to convert from g to mol of solute.
Then, plug your answer into the molarity equation:
1 mol NaCl
90.0 g NaCl =
1.54 mol NaCl
58.5 g NaCl
mol solute
1.54 mol
0.440 mol/L
Molarity (M) = = =
L solution
3.50 L

20. Molarity Calculations Sample Problem B
Chapter 12 – Section 3: Concentration of Solutions
Molarity Calculations Sample Problem B
You have 0.8 L of a 0.5 M HCl solution. How many moles of HCl does this solution contain?
Solution:
First, write out M as moles/Liter:
Then, multiply by the L of solution:
mol solute
0.5 mol HCl
Molarity (M) = =
L solution
1 L
0.5 mol HCl
0.8 L =
0.4 mol HCl
1 L

21. Molarity Calculations Sample Problem C
Chapter 12 – Section 3: Concentration of Solutions
Molarity Calculations Sample Problem C
How many grams of solute are needed to make L of a 1.75 M solution of Ba(NO3)2?
Solution:
Multiply Molarity by L of solution to get mol of solute:
Then, convert from mol to g by using molar mass:
1.75 mol Ba(NO3)2
2.50 L =
4.38 mol Ba(NO3)2
1 L
261.3 g Ba(NO3)2
1,140 g Ba(NO3)2
4.38 mol Ba(NO3)2 =
1 mol Ba(NO3)2

22. Chapter 12 – Section 3: Concentration of Solutions
Molality
Molality is the concentration of a solution expressed in moles of solute per kilogram of solvent.
The symbol for molality is m.
moles of solute
molality (m) =
kilograms of solvent

23. Molality Calculations Sample Problem A
Chapter 12 – Section 3: Concentration of Solutions
Molality Calculations Sample Problem A
Find the molal concentration of a solution prepared by dissolving 17.1 g of sucrose (C12H22O11) in 125 g of water.
Solution:
First, you need to convert from g to mol of solute.
Convert g of water to kg by dividing by 1000.
Then, plug the numbers into the molality equation:
1 mol C12H22O11
mol C12H22O11
17.1 g C12H22O11 =
342.0 g C12H22O11
mol solute
mol
0.400 mol/kg
molality (m) = = =
kg solvent
0.125 kg

24. Molality Calculations Sample Problem B
Chapter 12 – Section 3: Concentration of Solutions
Molality Calculations Sample Problem B
How many grams of solute are needed to make a m solution of HNO3 in 2.00 kg H2O?
Solution:
Multiply molality by kg of H2O to get mol of solute:
Then, convert from mol to g by using molar mass:
1.50 mol HNO3
2.00 kg H2O =
3.00 mol HNO3
1 kg H2O
63.0 g HNO3
3.00 mol HNO3 =
189 g HNO3
1 mol HNO3

25. Ions in solutions and Colligative Properties
Chapter 13
Ions in solutions and Colligative Properties

26. Chapter 13 – Section 1: Compounds in Aqueous Solutions
Dissociation
Dissociation is the separation of ions that occurs when an ionic compound dissolves.
Examples:
NaCl(s) → Na+(aq) + Cl-(aq)
CaCl2(s) → Ca2+(aq) + 2 Cl-(aq)
H2O
1 mole
1 mole
1 mole
H2O
1 mole
1 mole
2 moles

27. Dissociation Sample Problem
Chapter 13 – Section 1: Compounds in Aqueous Solutions
Dissociation Sample Problem
a.) Write the equation for the dissolution of aluminum sulfate, Al2(SO4)3 , in water. b.) How many moles of aluminum ions and sulfate ions are produced by dissolving 1 mol of Al2(SO4)3? c.) What is the total number of moles of ions produced by dissolving 1 mol of Al2(SO4)3?
H2O
Al2(SO4)3(s) 2
Al3+(aq)
+ SO42-(aq) 3
1 mole
2 moles
3 moles
2 moles aluminum ions & 3 moles sulfate ions
5 moles total ions

28. Colligative Properties
Chapter 13 – Section 2: Colligative Properties of Solutions
Colligative Properties
Properties that depend on the concentration of solute particles but not on their identity are called colligative properties.
Colligative properties include:
Vapor-Pressure Lowering
Freezing-Point Depression
Boiling-Point Elevation

29. Vapor-Pressure Lowering
Chapter 13 – Section 2: Colligative Properties of Solutions
Vapor-Pressure Lowering
A nonvolatile substance has little tendency to become a gas under existing conditions.
The vapor pressure of a solvent is lower when a nonvolatile substance is added to it.
This causes the solution to be liquid over a larger temperature range, lowering the freezing point and raising the boiling point.

30. Freezing-Point Depression
Chapter 13 – Section 2: Colligative Properties of Solutions
Freezing-Point Depression
Freezing-Point Depression – the lowering of the freezing point of a solution compared to the pure solvent; proportional to the molal concentration of the solution.

31. Boiling-Point Elevation
Chapter 13 – Section 2: Colligative Properties of Solutions
Boiling-Point Elevation
Boiling-Point Elevation – the raising of the boiling point of a solution compared to the pure solvent; proportional to the molal concentration of the solution.
Visual Concept