1. Section 3: Factors Affecting Solvation
Factors such as temperature, pressure, and polarity affect the formation of solutions. K
What I Know W
What I Want to Find Out L
What I Learned

2. 10(B) Develop and use general rules regarding solubility through investigations with aqueous solutions.
10(A) Describe the unique role of water in chemical and biological systems.
10(E) Distinguish between types of solutions such as electrolytes and nonelectrolytes and unsaturated, saturated, and supersaturated solutions.
10(F) Investigate factors that influence solubilities and rates of dissolution such as temperature, agitation, and surface area.
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Factors Affecting Solvation

3. Essential Questions How do intermolecular forces affect solvation?
What is solubility?
Which factors affect solubility?
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Factors Affecting Solvation

4. Vocabulary Review New exothermic solvation heat of solution
unsaturated solution
saturated solution
supersaturated solution
Henry’s law
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Factors Affecting Solvation

5. The Solvation Process
Solvation is the process of surrounding solute particles with solvent particles to form a solution.
Solvation in water is called hydration.
The attraction between dipoles of a water molecule and the ions of a crystal are greater than the attraction among ions of a crystal.
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Factors Affecting Solvation

6. The Solvation Process
The overall energy change that occurs during solution formation is called the heat of solution.
Sucrose molecules have several O–H bonds, which become sites for hydrogen bonding with water molecules.
Oil does not form a solution with water because there is little attraction between polar water molecules and nonpolar oil molecules.
During solvation, the solute must separate into particles and move apart, which requires energy.
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Factors Affecting Solvation

7. Factors That Affect Solvation
Stirring or shaking moves dissolved particles away from the contact surfaces more quickly and allows new collisions to occur thereby increasing the rate of solvation.
Breaking the solute into small pieces increases surface area and allows more collisions to occur thereby increasing the rate of solvation.
As temperature increases, rate of solvation increases.
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Factors Affecting Solvation

8. Solubility
Unsaturated solutions are solutions that contain less dissolved solute for a given temperature and pressure than a saturated solution.
Saturated solutions contain the maximum amount of dissolved solute for a given amount of solute at a specific temperature and pressure.
Solubility depends on the nature of the solute and solvent.
Solubility is affected by increasing the temperature of the solvent because the kinetic energy of the particles increases.
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Factors Affecting Solvation

9. Solubility
A supersaturated solution contains more dissolved solute than a saturated solution at the same temperature.
To form a supersaturated solution, a saturated solution is formed at high temperature and then slowly cooled.
Supersaturated solutions are unstable.
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Factors Affecting Solvation

10. Solubility Factors Affecting Solvation
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Factors Affecting Solvation

11. Solubility
Henry’s law states that at a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P).
Gases are less soluble in liquid solvents at high temperatures.
Solubility of gases increases as its external pressure is increased.
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Factors Affecting Solvation

12. HENRY’S LAW Problem Response
Use with Example Problem 5.
Problem
If 0.85 g of a gas at 4.0 atm of pressure dissolves in 1.0 L of water at 25°C, how much will dissolve in 1.0 L of water at 1.0 atm of pressure and the same temperature?
KNOWN
UNKNOWN
S1 = 0.85 g/L
S2 = ? g/L
P1 = 4.0 atm
P2 = 1.0 atm
Response
ANALYZE THE PROBLEM
You are given the solubility of a gas at an initial pressure. The temperature of the gas remains constant as the pressure changes. Because decreasing pressure reduces a gas’s solubility, less gas should dissolve at the lower pressure.
SOLVE FOR THE UNKNOWN
State Henry’s law.
S1 P1 = S2 P2
Solve Henry’s law for S2.
S2 = S1 P2 P1
Factors Affecting Solvation
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13. HENRY’S LAW SOLVE FOR THE UNKNOWN (continued) EVALUATE THE ANSWER
Substitute S1 = 0.85 g/L, P1 = 4.0 atm, and P2 = 1.0 atm. Multiply and divide numbers and units.
S2 = g 1.0 L atm 4.0 atm = 0.21 g/L
EVALUATE THE ANSWER
The solubility decreased as expected. The pressure on the solution was reduced from 4.0 atm to 1.0 atm, so the solubility should be reduced to one-fourth its original value, which it is. The unit g/L is a solubility unit, and there are two significant figures.
Factors Affecting Solvation
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14. Review Essential Questions Vocabulary
How do intermolecular forces affect solvation?
What is solubility?
Which factors affect solubility?
Vocabulary
solvation
heat of solution
unsaturated solution
saturated solution
supersaturated solution
Henry’s law
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Factors Affecting Solvation