1. Molarity
Essential Question: How do chemists determine the strength of solutions?

2. Kool-Aid Science
What is the solute and the solvent in your Koo-Aid solution?
Solute – the mix Solvent - the water
How strong is your solution?
Is it dilute or concentrated?

3. Concentration What does it mean when a solution is concentrated?
It means that a lot of solute is dissolved in the solution

4. Dilute What does it mean when a solution is dilute?
It means that there is not a lot of solute dissolved in the solvent

5. What the Problem? Concentrated and dilute are relative
Think about coffee
What is strong to one person is not strong to another
These terms do not give a precise description of the solution
We need a need new unit of measurement

6. Molarity Molarity is defined as
Moles (that’s right moles again) divided by liters
.5M means .5 moles per liter
Molarity is the number of moles of solute dissolved in volume of solvent measured in liters
Molarity can also be written in brackets
[2.5] means 2.5 moles per liter
The molarity is 2.5

7. Example
What is the molarity of a solution that has 1 mole of salt dissolved in 500 ml of water
First convert ml into liters
500 ml x 1L/1,000 ml = .5L
Divide moles by liters
1mole/.5L = 2M

8. Another Example
What is the molarity of a solution that has 31 grams of HNO3 in 250 ml of water.
31 x 1 mole/63 grams = .49 moles
250 ml x 1 liter/1,000 ml = .25 liters
.49 moles/.25 liters = 1.96 M