1. Table of Contents
Chapter 15: Solutions

2. Some Helpful Definitions
Solutions: Basic Concepts
Some Helpful Definitions
solute –dissolved substance, may change phase, lesser amount
solvent – dissolving, no phase change, greater amount
soluble – the ability of a solute to dissolve.
insoluble – a solute unable to dissolve.
predicting solubility: “like dissolves like.”

3. Concentrated Versus Dilute
Solutions: Basic Concepts
Concentrated Versus Dilute
Chemists never apply the terms strong and weak to solution concentrations.
These terms are used to describe the chemical behavior of acids and bases.
Instead, use the terms concentrated and dilute.

4. Percent by mass or volume Percent by volume
Solutions: Basic Concepts
Concentration
Concentration units:
Percent by mass or volume
Percent by volume
Molality
Molarity

5. Percent by mass = mass of solute x 100 mass of solution
Solutions: Additional Concepts
Concentration
Percent by mass = mass of solute x 100
mass of solution
Calculate the percent by mass of 2.56 g NaCl dissolved in 74 g water.
Mass solute: g
Mass solution: g NaCl + 74 g H2O = g
Percent by mass = g x 100 = 3.34 %
76.56 g

6. Percent by mass = mass of solute x 100 mass of solution
TRY IT OUT!
Concentration
Percent by mass = mass of solute x 100
mass of solution
Calculate the percent by mass of 4.95 g NaCl dissolved in 53 g water.
Mass solute: g
Mass solution: g NaCl + 53 g H2O = g
Percent by mass = g x 100 = 8.54 %
57.95 g

7. Percent by volume = volume of solute x 100 volume of solution
Solutions: Additional Concepts
Concentration
Percent by volume = volume of solute x 100
volume of solution
Calculate the percent by volume of 26 mL methanol dissolved in 71 mL water.
Volume solute: 26 mL
Volume solution: 26 mL methanol + 71 ml H2O = 97 mL
Percent by mass = mL x 100 = 26.8 %
97 mL

8. Molality (m) = moles of solute kg solvent
Solutions: Additional Concepts
Concentration
Molality (m) = moles of solute kg solvent
What is the molality of 17.1 g NaCl in g H2O?
Moles solute: g NaCl
1 mol NaCl =
.2926
mol NaCl
58.44 g NaCl
Kilograms solvent: g H2O = kg H2O
Molality =
.2926 mol = 2.89 m
.1014 kg

9. Molality (m) = moles of solute kg solvent
TRY IT OUT!
Concentration
Molality (m) = moles of solute kg solvent
What is the molality of 21.3 g NaCl in 94.1 g H2O?
Moles solute: g NaCl
1 mol NaCl =
.3645
mol NaCl
58.44 g NaCl
Kilograms solvent: g H2O = kg H2O
Molality =
.3645 mol = 3.87 m
.0941 kg

10. Molarity (M) = moles of solute liters of solution
Solutions: Additional Concepts
Concentration
Molarity (M) = moles of solute
liters of solution
What is the molarity of 1.1 mol KCl in 1.8 L solution?
Moles solute: 1.1 mol
Liters solution: 1.8 L
Molarity =
1.1 mol = .61 M = .61 mol/L
1.8 L

11. Molarity (M) = moles of solute liters of solution
TRY IT OUT!
Concentration
Molarity (M) = moles of solute
liters of solution
What is the molarity of 2.4 mol KCl in .9 L solution?
Moles solute: 2.4 mol
Liters solution: .9 L
Molarity =
2.4 mol = 2.67 M = 2.67 mol/L
.9 L

12. Molarity (M) as a conversion factor
Solutions: Additional Concepts
Concentration
Molarity (M) as a conversion factor
How many grams of solute are in 68.0 mL M KOH?
68.0 mL KOH
1 L
mol KOH
56.11 g KOH
1000 mL
1 L
1 mol KOH =
.1278
g KOH
Use molarity as a conversion factor

13. Molarity (M) as a conversion factor
TRY IT OUT!
Concentration
Molarity (M) as a conversion factor
How many grams of solute are in 52.0 mL 0.12 M KOH?
52.0 mL KOH
1 L
.12 mol KOH
56.11 g KOH
1000 mL
1 L
1 mol KOH =
.350
g KOH
Use molarity as a conversion factor

14. Dilutions M1V1 = M2V2 (3.65 M NaOH) (V1) = (.95 M NaOH) (125 mL NaOH)
Solutions: Additional Concepts
Dilutions
M1V1 = M2V2
How many millimeters of 3.65 M NOH is needed to make 125 mL of 0.95 M NaOH solution?
(3.65 M NaOH)
(V1) =
(.95 M NaOH)
(125 mL NaOH)
(V1) =
36.1
mL NaOH

15. Dilutions M1V1 = M2V2 (2.75 M HCl) (V1) = (.65 M HCl) (80 mL HCl) (V1)
TRY IT OUT!
Dilutions
M1V1 = M2V2
How many millimeters of 2.75 M HCl is needed to make 80 mL of 0.65 M HCl solution?
(2.75 M HCl)
(V1) =
(.65 M HCl)
(80 mL HCl)
(V1) =
18.9
mL HCl

16. Your time! Worksheet: Do not do #4, #7, #10
Answers are posted at the front – CHECK IT!
Do as much as you can - due tomorrow at the beginning of class