1. BELLWORK 4/6/2017

2. ANSWER – B

3. BELLWORK #2

4. ANSWER - J

5. BELLWORK #3

6. ANSWER - H

7. BELLWORK #4

8. ANSWER - A

9. Molarity and Molality
Chapter 12

10. Molarity
Chemists describe solutions in terms of concentration. We define the concentration of a solution as the amount of solute in a given volume of solution.
The most commonly used expression of concentration is molarity (M).
Molarity is defined as the number of moles of solute dissolved in a liter of solution.
A 1.0 M solution contains 1.0 mol of solute per liter of solution

11. Molarity – (M) Molarity is calculated using the following equation:
What does this mean for you?
Set-up these problems using dimensional analysis
If you’re given grams, you have to convert grams to moles
If you’re given mL, you have to convert mL to L ( 1L =1000mL)
M (molarity) = moles of solute M= mol
liters of solution L

12. Molarity Example 1
5.7 g KNO3 dissolves in a 233 mL solution. What is molarity?
Convert grams to moles
Convert mL to L
Divide mol/L
5.7 g KNO3 1 mol KNO3 = mol KNO3
g KNO3
233 mL 1 L = L
1000 mL
0.056 mol KNO3
0.233 L = 0.24 M KNO3

13. Molarity Example 2
Calculate the molarity of a solution that has 11.5 g of NaOH dissolved in 1500 mL of solution
Convert grams to moles
Convert mL to L
Divide mol/L
11.5 g NaOH 1 mol NaOH = mol NaOH
40.0 g NaOH
1500 mL 1 L = 1.5 L
1000 mL
0.288 mol NaOH
1.5 L = 0.19 M NaOH

14. Molality
Molality(m) = Moles of Solute / Kg of Solvent

15. Molality Example Example #1 –
Suppose you had 2.00 moles of solute dissolved into 1.00 L of solvent. What's the molality?

16. ANSWER – 2.00 moles
1L = 1kg

17. EXAMPLE #2
What is the molality when 0.75 mol is dissolved in 2.50 L of solvent?

18. ANSWER moles
1L = 1kg
2.50 L = 2.50 kg

19. Now You Try…
3) Calculate the molality of 25.0 grams of KBr dissolved in mL pure water.

20. ANSWER 3 Convert 25 g of KBr to moles : 25g x 1 mole = .210 mol
Convert mL to L: mL x 1L = L
1000mL
Convert L to kg: L = kg
Divide moles /kg: mol
.750 kg
molality = m (

21. CLASSWORK / HOMEWORK: CH.12 WKSHT #2