1. Solution Concentration
A measure of how much solute is dissolved in a specific amount of solvent or solution.
Described qualitatively using “dilute” and “concentrated”
Can be calculated quantitatively by mass (molarity) or by volume (molality)
Can also be expressed as a percent – either percent by mass or percent by volume

2. Solution Concentration
If the solute is a solid being dissolved in a liquid, usually use molarity or % by mass
If the solute is a liquid being dissolved in a liquid, usually use molality or % by volume

3. Percent Concentration
Percents are a ratio of the amount of solute over the total amount of solution times 100%
The amount can be measured in mass or volume but both measurements must be the same unit

4. Try It
A salt water aquarium must maintain a sodium chloride solution similar to ocean water which is 3.6 g NaCl per g of water. What is the % by mass of NaCl in the solution?
3.6 / ( ) X 100%
= 3.5%

5. Try It
Isopropyl rubbing alochol is usually 70% alcohol and 30% water. If you have 750 ml of rubbing alcohol, how much is isopropyl alcohol and how much is water?
.70 x 750 ml = 525 ml of alcohol
.30 x 750 ml = 225 ml of water

6. Molarity
One of the most common ways to describe concentration quantitatively
Also called molar concentration
Abbreviated with a capital M (yes, just like Molar Mass)
Calculated by dividing the moles of solute by the liters of solution
Label is moles per liter or M

7. Try It
You have a 100 ml sample of an aqueous solution that contains .085 moles of KCl. What is it’s molarity?
100 ml x 1l / 1000 ml = .100 L
.085 molKCl / .100 L = .85 mol/L or .85M

8. Preparing a Molar Solution
How many grams of sucrose (C12H22O11) is needed to prepare one liter of a 1.50 M solution?
You’ll need the molar mass of sucrose:
1.5 mol g
_____________ X ___________ = 513 g / liter
1 liter mol

9. Preparing a Molar Solution
How many grams of sucrose (C12H22O11) is needed to prepare 100 mL of a 1.50 M solution?
1.5 mol g
_____________ X ___________ = 513 g / liter
1 liter mol
1 L g
100 mL X __________ X _____________ = 51.3 g
1000 mL L