1. Solutions
Chapter 12.2

2. Henry’s Law
Henry’s Law- as the pressure (P) of the gas above a liquid increases the solubility (S) of gas increases. (And vice versa)
S1=S2
P1 P2
Example: If the soulubility of a gas in water is 0.77 g/L at 3.5 atm of pressure, what is its solubilty at 1.0 atm of pressure?

3. Henry’s Law- Practice
Example: If the soulubility of a gas in water is 0.77 g/L at 3.5 atm of pressure, what is its solubilty at 1.0 atm of pressure?
S1=S or
P1 P2
S2 = S1 x P2 = P1
S2 = 0.77g/L x 1.0 atm =
3.5 atm
= 0.22g/L

4. How many grams of KCl are required to saturate 100 g of water at 10 C?

5. Concentration of Solutions
Concentration—measurement of how much solute is in a given amount of solvent.
Diluted solution—a relatively small amount of solute.
Concentrated solution—a relatively large amount of solute.
These are not very definite terms.

6. Measuring Concentration
Molarity (M)-number of moles of solute in 1 L of solution.
M= Moles solute
Liters solvent
4.0 moles of LiCl is dissolved in 5.0 liters of water. What is the molarity of the solution?
4.0 moles LiCl = 0.8 M LiCl
5.0 liters H2O

7. Molarity Practice
1) 6.0 mol of MgCl2 is dissolved in 20.0 L of water. What is the molarity of the solution?
6.0 mol MgCl2 = 0.3 M MgCl2
20.0 L H2O

8. Molarity Practice
2) 10.0g of NaCl is dissolved in 5.0L of water. What is the molarity of the solution?
convert grams to moles!!
10.0g NaCl x __1 mol__ = 0.172mol NaCl
58 g NaCl
0.172 mol NaCl = M NaCl
5.0L H2O

9. 3) What is the molarity of a salt solution made by dissolving
3) What is the molarity of a salt solution made by dissolving .28 g of NaCl in 2.00 mL of water? Assume the final volume of the solution is the same as the volume of the water. (convert mL to L and moles )
2.40 M

10. Molality Molality (m or μ )= Moles solute Kg solvent
Molality—a way to express the solute to solvent ratio, molal concentration.
Symbol=μ or cursive lower case m
Number of moles of solute dissolved in 1 kg of solvent.
Molality (m or μ )= Moles solute
Kg solvent

11. Practice problems Molality (m) Moles solute Kg solvent
1) If you add 0.5 mol of sugar (C6H12O6) to 2.0Kg of water what is the molality?
0.25 m or μ

12. 2) Determine the molality of a solution of 560 g of acetone, CH3COCH3, in 620 g of water.
Remember- 1kg=1000g
15.5 m or μ

13. 3) What is the molality of a solution of 12
3) What is the molality of a solution of 12.9 g of fructose, C6H12O6, in 31.0 g of water?
2.31 μ

14. Making Dilutions M1V1= M2V2 M=Molarity & V=Volume
1) Dilute 1.0L of 5.0 M SrS to 2.0M. What is the final volume?
(5.0 M SrS)(1.0L) = (2.0M SrS)(V2)
V2 = 2.5 L
How much water would you need to add?
If the total volume = 2.5L & original volume is 1.0L
Need to add 1.5L of water to make the dilution

15. Let’s Practice
2) How would you prepare 100. mL of a M HNO3 solution if you have a 12.0 M stock solution of HNO3?
M1V1=M2V2
M1=12.0 M
V1=?
M2=0.500 M
V2=100.mL
V1=4.17 mL
Amount of water added to V1=95.83 mL

16. Solubility Guidelines
Table 1 page 437

17. Classwork & Homework
Molality problems- page 7 (check answers at bottom)
Molarity Problems- Page 8