Unit 8 - Kinetics & Equilibrium - Regents Flashcards
1
Q
Definition of Kinetics
A
At what rate does a chemical reaction occur?
2
Q
Definition of Collision Theory (3)
A
- A reaction will most likely occur if
- Reactant Particles Collide
- With proper energy & orientation.
3
Q
What are the 6 factors affecting the rate of a reaction?
A
- Nature of Reactants
- Concentration
- Surface Area
- Pressure
- Catalyst
- Temperature
4
Q
How does the nature of reactants affect the rate of a reaction? (5)
A
- Breaking bonds require Activation Energy
- Slower reaction rate will occur
- Covalent Bonds break slower than Ionic Bonds
- Covalent shares e-, forming bonds
- Ionic bonds are from electrostatic attraction of opp. charges
5
Q
How does concentration affect the rate of a reaction? (3)
A
- Higher Concentration = More Atoms
- More Atoms = More Collisions
- More Collisions = Faster Rxn
6
Q
How does surface area affect the rate of a reaction? (4)
A
- Higher SA = More Exposed Areas
- More Exposed Areas = More Possible Areas for Collision
- More Possible Areas for Collision = More Collisions
- More collisions = Faster Rxn
7
Q
How does pressure affect the rate of a reaction? (4)
A
- Only applies to gases
- Hi Pressure has same effect as Hi Concentration
- Gas particles are closer together, increasing collisions
- More Collisions = Faster Rxn
8
Q
How do catalysts affect the rate of a reaction?
A
Catalysts provide an alternate pathway with a lower activation energy
9
Q
How does temperature affect the rate of a reaction? (3)
A
- Temperature is the average kinetic energy of particle
- Faster Particles = More Collisions
- More Collisions = Faster Rxn
10
Q
When is there a chemical change in compounds? (2)
A
- Compounds are formed or decomposed
- Reactant disappear and products appear
11
Q
What happens to energy when bonds break and form? (3)
A
- When bonds break, energy is absorbed
- It takes energy to break bonds
- When bonds form, energy is released
12
Q
Definition of Enthalpy (3)
A
- Amount of heat absorbed or released
- DURING A CHEMICAL CHANGE
- Measured in Joules
Δ H
13
Q
How is Enthalpy Calculated?
A
ΔH = Enthalpy of the Product - Enthalpy of Reactant
14
Q
Definition of Exothermic Reactions (5)
A
- Products have less E than reactants
- During a chemical rxn, extra E is released
- ΔH is negative
- Freezing & Condensation
- System is cooling down but surroundings are heating up
15
Q
Definition of Endothermic Reactions (5)
A
- Reactants have more E than products
- During a chemical rxn, extra E is absorbed from surroundings
- ΔH is positive
- Melting & Boiling
- System is heating up but surroundings are cooling down
16
Q
How do you read a PE Diagram? (6)
A
- Reactants are on the far left
- Products are on the far right
- Activation Complex is the peak
- Activation Energy (Forward Rxn) is vertical distance of peak & reactant
- Activation Energy (Reverse Rxn) is vertical distance of peak & product
- Enthalpy - Difference of Product & Reactant
- Dotted Lines Indicate a Catalyst
- Lowered Activation Energy
- PE of Product & Reactant stay the same
- ΔH is the same
17
Q
What does Activation Energy ensure?
A
When molecules collide, they have enough energy for an effective collision
18
Q
Definition of Equilibrium (5)
A
- Dynamic Process
- RATE of forward rxn = RATE of reverse rxn
- Can only occur in a closed system
- Concentrations are constant, not =
- No observable changes occur
19
Q
Definition of Constant Concentration (3)
A
- Reactant & Product Concentration remain unchanged
- Once Equilibrium is Reached (= rates of forward & reverse rxn)
- Constant Activity but no Net - Change in Overall Amount
20
Q
Definition of Closed System
A
Products & Reactants Cannot Leave or Enter the System
21
Q
What are two types of equilibrium?
A
- Physical Equilibrium
- Chemical Equilibrium
22
Q
What are two types of Physical Equilibrium (2)
A
- Phase Equilibrium
- Solution Equilibrium
23
Q
Definition of Physical Equilibrium
A
Equilibrium is established during a physical change
24
Q
Definition of Solution Equilibrium (5)
A
- Saturated Solutions are at Equillibrium
- Only occurs when more solute is added to a sat. solution
- No more solute can dissolve in a saturated solution
- So, some solute must recrystallize to allow it to dissolve
- Rate of dissolution = Rate of recrystallization
25
Definition of Phase Equilibrium (4)
1. Equilibrium during a phase change
2. Melting/Freezing & Evaporation/Condensation
3. At 0°C, in a closed container, rate of freezing = rate of melting
4. At 100°C in a closed container, rate of evaporation = rate of condensation
26
How can Solution Equilibrium shift? (3)
1. Temperature/Pressure Changes (Stress)
2. Rate of Dissolution > Rate of Recrystallization
3. Continues until solution saturates at equillbrium
27
Definition of Chemical Equilibrium (2)
1. Equilibrium at a Chemical Change
2. Observable changes (color/pressure/temp.) will not occur
ex:
- Even though a rxn w/ a color change still occurs at a molecular level
- No color & macroscopic changes occur once equilibrium is established
- Bc of constant concentration of reactants & products
28
Definition of Le Châtelier's Principle (3)
1. A stress on a system at equilibrium
2. Will change/shift the equilibrium
3. To "relieve" stress
29
Definition of Stress (3)
1. Any change in conditions on a system
2. That affects the rate of a reaction
3. Temperature, Concentration, Pressure, etc.
30
What is the effect of a concentration change to a system of equilibrium? (5)
1. Increasing concentration of a substance
2. Causes the reaction to shift
3. To consume the substance
4. To decrease the increased change of concentration
5. To rebalance rxn at a new equilibrium
31
What is the effect of an increase in concentration of a reactant? (2)
1. The reaction will shift to produce products
2. In reversible rxns, the forward rxn will be favored
32
What is the effect of an increase in concentration of a product? (2)
1. The reaction will shift to produce reactants
2. In reversible rxns, the reverse rxn will be favored
33
What is the effect of an increase in temperature in a system of equilibrium? (3)
1. The reaction will shift to favor the endothermic reaction
2. BC it wants to absorb the extra heat that was added
3. Consider heat as a product/reactant (you can use same logic as conc)
34
What is the effect of a decrease in temperature in a system of equilibrium? (3)
1. The reaction will shift to favor the exothermic reaction
2. There's less heat to absorb, so endo rxn cannot perform at a faster rate
3. Consider heat as a product/reactant (you can use same logic as conc)
35
What is the effect of a pressure increase in a system of equilibrium? (2)
1. Only matters if there's unequal moles of gases on both sides of rxn
2. Reaction will shift to the side of rxn that produces fewer moles
36
What is the effect of a pressure decrease in a system of equilibrium? (2)
1. Only matters if there's unequal moles of gases on both sides of rxn
2. Reaction will shift to the side of rxn that produces more moles
37
What is the effect of a concentration, temperature, & pressure change to Haber's equation
N2 (g) + 3H2 (g) ⇌ 2NH3 (g) + heat
(3/2/2)
Concentration
1. Increasing Conc. of N2 or H2 will produce more NH3
2. Increasing Conc. of NH3 increases rate of decomposition, producing more N2 & H2
3. (When increasing H, N decreases bc N will be used at faster rate with lower conc.)
Temperature
1. Increasing temp. favors reverse rxn & production of N & H (endothermic)
2. Decreasing temp. favors forward rxn & production of NH3 (exothermic)
Pressure
1. Increasing pressure favors forward rxn & production of NH3 (fewer moles)
2. Decreasing pressure favors reverse rxn & production of N & H (more moles)
38
What is the effect of a catalyst on a system of equilibrium? (3)
1. Does not shift equilibrium
2. Increases rate of both forward & reverse rxn
3. Also allows the system to reach equilibrium more quickly
