1. Thermochemistry: The heat energy of chemical reactions
• Enthalpy is the amount of ________ transferred during a reaction. The symbol for the change in enthalpy is ∆H.
An endothermic reaction is one that ___________ heat from the surroundings. (___ ∆ H) An endothermic reaction feels ______.
Example--an “instant” ice pack
• An exothermic process is one that _____________ heat to the surroundings. (___ ∆ H) An exothermic reaction feels _____.
Example--burning paper
gains +
cold
loses –
hot

2. Phase Changes & Energy
Endothermic: melting, evaporating/boiling & sublimation
Exothermic: freezing, condensation, & deposition

3. Endothermic
Exothermic

5. Chemical Kinetics fast concentration Temperature Enzymes Surface
Kinetics is the study of how _____ chemical reactions occur.
There are 4 important factors which affect rates of reactions:
reactant ______________
________________
action of catalysts (________________are biological catalysts.)
___________ area
For the reaction “A  B” there are two ways of measuring rate:
(1) the speed at which the reactants ____________
(2) the speed at which the products __________
In general, rates of reactions _________ as concentrations increase since there are more _____________ occurring between reactants.
concentration
Temperature
Enzymes
Surface
disappear
appear
increase
collisions

6. Catalysts and Reaction Rates

8. Chemical Equilibrium equals dynamic constant
Some reactions are reversible, so as products accumulate they can begin to turn back into reactants.
When the rate of the forward reaction ____________ the rate of the reverse reaction, it is at equilibrium.
Here’s an example:
Each is constantly being formed at the same rate that it is being consumed. It is therefore called a “_____________ equilibrium”.
Chemical equilibrium is the point at which the concentrations of all species are ________________.
equals
dynamic
constant

9. Dynamic Equilibrium

10. Changes in Equilibrium
Le Chatelier’s Principle: If a stress is applied to a system that is already at equilibrium, the equilibrium will shift to reduce the effect of the stress.
We will now look at changing various things on a system at equilibrium.
Consider this reaction: A + B C + D
Here are some things that one can change in order to shift the equilibrium:
(1) Changing _______________________ of the Solutions
(2) Changing the _____________________ of the Gases
(3) Changing the _____________________
Adding a catalyst ________ _______shift the equilibrium. It just makes the reaction achieve equilibrium ______________.
Concentration
Pressure
Temperature
does not
faster

11. Changes in Equilibrium
For the reaction below, predict the direction the equilibrium will shift given the following changes. Temperature and volume are held constant.
Fe3+(aq) + SCN–1(aq) FeSCN2+(aq)
(colorless) (red)
More Fe3+ is added to the reaction. ____________________
NO2 (g) + 7 H2 (g) ↔ 2 NH3 (g) + 4 H2O(g)
Predict the shift in equilibrium given the following changes:
a. addition of ammonia ____________________
b. removal of nitrogen dioxide ____________________
c. removal of water vapor ____________________
d. addition of a catalyst ____________________
Shifts to the right (…more red)
Shifts to the left
Shifts to the left
Shifts to the right
No change

12. Catalysts & Changes in Equilibrium