1. Colligative Properties of Solutions
Reaction Rates…
How can I make a reaction happen faster?

2. What is a colligative property?
A property that depends on:
the concentration of solute particles in solution
the solvent used
A colligative property does not depend on:
1. the identity of the solute

3. Dilute Versus Concentrated Solutions
Dilute--> a low amount of solute is dissolved in a solvent
Concentrated--> a high amount of solute is dissolved in a solvent
These terms will not tell us whether a solution is saturated, unsaturated, or supersaturated
The concentration of a solution can be found using the Molarity (M) and Molality (m) equations

4. Freezing Point Depression
When a solute is dissolved in a solvent, the freezing point of the solvent will depress (become lower) than the normal freezing point of the pure solute

5. What does the FP depression depend on?
The amount the FP will be lowered depends on 3 factors:
The concentration of the solution
Higher molality (m) = higher depression
Whether or not the solution is an electrolyte
Electrolytes = higher depression
The identity of the solvent used
H2O vs. C2H5OH will exhibit different depressions

6. Practical Application of FP Depression
Why does putting salt on the roads when it is icy prevent the roads from being slick?
The addition of salt as a solute will lower the FP of H2O and help to prevent ice from forming

7. What Factors Affect the Rate of a Reaction?
1. Increase in surface area
Ex. Increasing the surface area of a substance allows for more particle contact and collisions, therefore increasing the rate of a reaction
Granulated sugar should dissolve more quickly in a solvent because of its greater surface area

8. 2. Increase in temperature
Ex. Increasing the temperature of a reaction allows for more frequent particle contact and collisions due to an increase in the kinetic energy of the system, therefore increasing the rate of a reaction

9. 3. Increase in concentration of reactants
Ex. Increasing the concentration of reactants allows for more particle collisions because there are more particles present, therefore increasing the rate of a reaction

10. 4. Addition of a catalyst
Ex. The addition of a catalyst will force the particles to come in contact at a quicker rate, therefore increasing the rate of the reaction
• 5. Agitation/Stirring

11. The Collision Theory
In order for a reaction to occur, 2 particles must have an effective collision. A successful collision needs:
1. Proper orientation (particles must hit in the right spots)
2. Suitable kinetic energy (particles must hit with the right amount of speed --> too much or too little may result in an ineffective collision)

13. Reaction Rate Diagrams
Activation Energy (Ea) = the energy needed to get a reaction started
This diagram is representing an exothermic reaction because energy is being released and the products contain less energy than the reactants
Lowers Ea

14. Inhibitors increase Ea by slowing down a reaction