1. Chapter 12
Solutions
12.1 Types of Mixtures

2. Classification of Matter
Solutions are homogeneous mixtures!
Classification of Matter

3. Solute Solvent A solute is the dissolved substance in a solution.
Salt in salt water
Solute
A solute is the dissolved substance in a solution.
Carbon dioxide in soda drinks
Sugar in soda drinks
Solvent
A solvent is the dissolving medium in a solution.
Water in salt water
Water in soda

4. Types of Solutions Gaseous mixtures Air is a solution Solid solutions
Metal alloys
Liquid solutions
Liquid dissolved in a liquid
(alcohol in water)
Solid dissolved in a liquid
(salt water)

5. Concentrated vs. Dilute

6. Suspensions and Colloids
Suspensions and colloids are NOT solutions.
Suspensions: The particles are so large that they settle out of the solvent if not constantly stirred. Particles can be filtered out.
Example: Oil & Water
Colloids: The particles intermediate in size between those of a suspension and those of a solution. Particles cannot be easily filtered out.
Example: Milk

8. Gelatin is protein in water. Quicksand is sand in water
Mayonnaise is oil in water
Milk of Magnesia is a sol with solid magnesium hydroxide in water
Smoke is a solid in a gas.
Fog is a liquid in a gas.

9. The Tyndall Effect
Colloids scatter light, making a beam visible. Solutions do not scatter light.
Which glass contains a colloid?
colloid
solution

10. Electrolytes vs. Nonelectrolytes
The ammeter measures the flow of electrons (current) through the circuit.
If the ammeter measures a current, and the bulb
glows, then the solution conducts.
If the ammeter fails to measure a current, and the
bulb does not glow, the solution is non-conducting.

11. Definition of Electrolytes and Nonelectrolytes
An electrolyte is:
A substance whose aqueous solution conducts
an electric current.
A nonelectrolyte is:
A substance whose aqueous solution does not
conduct an electric current.
Try to classify the following substances as
electrolytes or nonelectrolytes…

12. Electrolytes?
Pure water
Tap water
Sugar solution
Sodium chloride solution
Hydrochloric acid solution
Lactic acid solution
Ethyl alcohol solution
Pure sodium chloride

13. Electrolytes: Nonelectrolytes: Tap water (weak) NaCl solution
HCl solution
Lactate solution (weak)
Pure water
Sugar solution
Ethanol solution
Pure NaCl
But why do some compounds conduct electricity in
solution while others do not…?

14. Chapter 12
Solutions
12.2 The Solution Process

15. Dissolution of sodium Chloride
The Hydration Process
Dissolution of sodium Chloride

16. Saturation of Solutions
A solution that contains the maximum amount of solute that may be dissolved under existing conditions is saturated.
A solution that contains less solute than a saturated solution under existing conditions is unsaturated.
A solution that contains more dissolved solute than a saturated solution under the same conditions is supersaturated.

18. Factors Affecting the Rate of Dissolution
Increasing the Surface Area of the Solute
Finely divided substances dissolve more rapidly
Agitating a Solution
Stirring or shaking brings solvent into contact with more solute particles
Added energy temporarily increases solubility
Heating
Heating almost always increasing the rate of dissolution of solids in liquids

19. “Like dissolves like” Polar substances dissolve in polar solvents
Nonpolar substances dissolve in nonpolar solvents
Examples:
Polar and ionic compounds are not soluble in nonpolar solvents
Fats, oils and many petroleum products are soluble in nonpolar solvents
Nonpolar solvents include CCl4 and toluene (methyl benzene), C6H5CH3

20. Liquid Solutes and Solvents
Immiscible - Liquid solutes and solvents that are not soluble in each other
Ex: Oil and water
Miscible - Liquids that dissolve freely in one another in any proportion
Ex: Benzene and carbon tetrachloride (both nonpolar)
Ex: Water and ethanol (both polar)
Hydrates
Ionic substances that incorporate water molecules into their structure during the recrystallization process
Ex: CuSO4•5H2O

22. Saturation and Equilibrium
The physical state in which the opposing processes of dissolution and crystallization of a solute occur at equal rates

23. Effects of Pressure on Solubility
Pressure has no real effect on the solubilities of liquids and solids in liquid solvents
Increasing pressure increases the solubility of gases in liquids
Henry's Law
The solubility of a gas in a liquid
is directly proportional to the
partial pressure of that gas on the
surface of the liquid
Effervescence
The rapid escape of a gas from a liquid in which it is dissolved

24. Effects of Temperature on Solubility
Solubility of solids increases with temperature
Solubility of gases decreases with temperature

25. Solubility Trends
The solubility of MOST solids increases with temperature.
The rate at which solids dissolve increases with increasing surface area of the solid.
The solubility of gases decreases with increases in temperature.
The solubility of gases increases with the pressure above the solution.

26. Therefore… Solids tend to dissolve best when: Heated Stirred
Ground into small particles
Liquids & Gases tend to dissolve best when:
The solution is cold
Pressure is high

27. Heat of Solution
The Heat of Solution is the amount of heat energy absorbed (endothermic, positive) or released (exothermic, negative) when a specific amount of solute dissolves in a solvent.
Substance
Heat of Solution
(kJ/mol)
NaOH
-44.51
NH4NO3
+25.69
KNO3
+34.89
HCl
-74.84

28. Chapter 12
Solutions
12.3 Concentration of Solution

29. Molarity (M)
The concentration of a solution measured in moles of solute per liter of solution.
mol = M L
Pronounced “molar”

32. Molality (m)
The concentration of a solution in moles of solute per kilogram of solvent.
mol = m kg
Since the most common solvent, water, has a density of 1 kg/L, one kilogram of water is the same as one liter of water!

33. Additional practice problems located in Appendix D p. 902
Dilutions
If a solution of known concentration and volume has been diluted, we can calculate the new concentration:
M1V1 = M2V2
Example:
20.00 mL of a M KBr solution is diluted to mL. What is the new molarity?
(20.00mL)(0.500M) = (100.00mL)(M2)
M2 =0.100 M
Additional practice problems located in Appendix D p. 902