1. CHAPTER 15
Solutions

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

3. Concentrated vs. Dilute

4. 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.

5. Saturation and Equilibrium

6. Solubility Rules
Reference Tables

7. Solubility Values
Solubility of a substance is the amount of that substance required to form a saturated solution with a specific amount of solvent at a specified temperature
The rate at which a substance dissolves does not alter the substances solubility

8. Factors that Affect Solubility
Temperature
Solubility of solids increases with temperature
Solubility of gases decreases with temperature
Pressure
has no real effect on the solubility of liquids and solids in liquid solvents
Increasing pressure increases the solubility of gases in liquids

9. Solubility Curves Each line represents a solute
Higher curves mean that the solute is more soluble, lower curves are less soluble
ABOVE the curve is SUPERsaturated, on the curve is saturated, and UNDER the curve is UNsaturated

10. Solubility Chart

11. 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.

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

13. Review Questions

14. A physical change occurs when
Problem 18
A physical change occurs when
A a peach spoils
B a bracelet turns your wrist green
C a copper bowl tarnishes
D a glue gun melts a glue stick

15. Problem 19
What substance has a melting point of -94°C and a boiling point of 65°C?
a. Ethanol
b. Chlorine
c. Hexane
d. Methanol

16. Problem 20
22.4 liters of a gas has a mass of 36.5 grams. What is the identity of the gas?
a. Chlorine
b. Hydrogen chloride
c. Nitrogen
d. Hydrogen

17. Day 2

18. Molarity and Dilutions

19. Heat of Solution
The Heat of Solution is the amount of heat energy absorbed (endothermic) or released (exothermic) when a specific amount of solute dissolves in a solvent.
Endothermic: absorbs heat so it feels cool
Exothermic: releases heat so it feels hot

20. Molarity mol of solute = M L of solution
The concentration of a solution measured in moles of solute per liter of solution.
mol of solute = M
L of solution

21. What is the molarity of 2.5 mol KCl in 1.0L solution?
Example
What is the molarity of 2.5 mol KCl in 1.0L solution?
M= mol L
M= 2.5mol 1L
M= 2.5M

22. What is the molarity of 0.96g MgCl2 in 500mL of solution?
Example 2
What is the molarity of 0.96g MgCl2 in 500mL of solution?
M= mol L
0.96g MgCl2 1mol MgCl2 = .01 mol MgCl2
95g MgCl2
M= .01 mol MgCl2
.500L
M= .02M

23. # of mol = molarity x L of solution
Example
How many moles of solute are contained in 15.25mL of a 2.1M solution of CaCl2?
M = mol L
# of mol = molarity x L of solution
# of mol = 2.1M (.01525L)
# of mol = .032 mol CaCl2

24. Practice Problems

25. What is the molarity of 1.35 mol H2SO4 in 245mL solution? M= 5.51M
Practice 1
What is the molarity of 1.35 mol H2SO4 in 245mL solution?
M= 5.51M

26. What is the molarity 9.33g Na2S in 450 mL solution? M= 0.27M
Practice 2
What is the molarity 9.33g Na2S in 450 mL solution?
M= 0.27M

27. Practice 3
How many moles of solute are contained in 125mL of a 0.050M solution of Ba(OH)2?
.00625mol

28. Practice 4
How many grams of solute are contained in 64.3mL of a M solution of KOH?
.0859g

29. Practice 5
How many grams of solute are contained in 142mL of a 1.4M solution of K2SO4?
34.6g

30. Moles of solute in the stock solution = moles of solute after dilution
Dilutions
Because the # of moles of solute does not change during a dilution
Moles of solute in the stock solution = moles of solute after dilution
M1V1=M2V2
M1V1 is the molarity and volume of the stock solution and M2V2 is the molarity and volume of the diluted solution

31. Example
How many milliliters of 2.55M NaOH is needed to make 125ml 0.75M NaOH?
M1V1 = M2V2
V1= M2V2 M1
V1=(.75)(125)
2.55
V1= 36.76L

32. Practice Problems

33. Practice 1
How would you prepare 500mL of 3 M HCl using 6 M HCl from the stockroom?
250mL

34. Practice 2
How much 12 M HCl must be used to prepare 500 ml of a 1 M HCl solution?
41.67mL

35. Molarity and Dilution Problems
Homework
Molarity and Dilution Problems

36. Review Questions

37. Problem 21
Which of the following substances best illustrates polar covalent bonding?
a. HCl
b. NaBr
c. CsF
d. Cl2

38. Problem 22
The methane, CH4, gas molecule exhibits what type of geometric shape?
a. trigonal planar
b. tetrahedral
c. bent or V-shaped
d. trigonal pyramidal

39. Problem 23
Which substance would have London dispersion forces as the main type of intermolecular forces of attraction?
a. H2O
b. F2
c. HCl
d. NaCl

40. Problem 24
Which of the following compounds is an exception to the octet rule?
a.BH3
b.CH4
c.NH3
d.H2O