Major Ideas: Rates And Equilibrium

Question 0

Equation for rxn rate

Answer 0

Change in quantity
_________________
Time interval

Question 1

How can the rate of rxn be determined?

Answer 1

By measuring the change in the amount of one of the reactants or one of the products in a given time interval

Question 2

What dis the slope of a quantity vs. time graph tells us

Answer 2

Rxn rate at particular time (gradient)

Question 3

3 conditions of collision theory

Answer 3

• particles must collide
• must collide with sufficient energy to react
• must collide at the correct orientation

Question 4

What is activation energy

Answer 4

Minimum energy required by colliding particles for a reaction to occur

Question 5

What is the transition state (a.k.a the activated complex)? (3points)

Answer 5

• highest potential energy state for the reacting system
• corresponds to some stage in rxn at which bond breaking and forming occur
• unstable (only temporary existence)

Question 6

What is the activation energy of a FORWARD rxn?

Answer 6

Energy difference between the transition state and reactants

Question 7

What is the change in enthalpy (^H)

Answer 7

Difference of potential energy (enthalpy) between reactants and products

Question 8

For an EXOTHERMIC rxn:

• relationship between products and reactants (energy)
• ^H value
• surrounding temperature (why?)

Answer 8

• products have LESS potential energy than reactants
• ^H is negative
• temperature of surrounding increase (releases heat)

Question 9

For an ENDOTHERMIC rxn:

• relationship between products and reactants (energy)
• ^H value
• surrounding temperature (why?)

Answer 9

• products have more potential energy than reactants
• ^H is positive (E.products-E.reactants)
• temperature of surroundings decrease (absorb heat)

Question 10

Factors that affect rxn rate:

1. Nature of reactants

Answer 10

Breaking covalent bonds requires more energy, therefore resulting in a slower rate than reactions just involving collision

Question 11

Factors that affect rxn rate:

2. Concentration

Answer 11

Higher concentration = more particles = more collisions = higher rate of rxn

Question 12

Factors that affect rxn rate:

3. Pressure

Answer 12

Higher pressure = less ‘space’ = more collisions = higher rate of rxn

Question 13

Factors that affect rxn rate:

4. Surface area

Answer 13

Bigger surface area = more particles exposed = moe collisions = higher rxn rate

Question 14

Factors that affect rxn rate:

5. Temperature

Answer 14

Increase temperature = increase Ek of particles = move faster = more collisions = higher rate of rxn

Question 15

Factors that affect rxn rate:

6. Catalyst

Answer 15

Provides alternative pathway for rxn = decreases activation energy = higher rate of rxn

Question 16

2 conditions for a system to be at equilibrium

Answer 16

• conc. of reactants and products present remain constant at all times
• rate of both forward and reverse rxns are equal

Question 17

What is an equilibrium constant?

Answer 17

• constant value representing rxn at particular temp.

Question 18

What I’d Le Châtelier’s principle?

Answer 18

A system at equilibrium that is subjected to change will adjust to re-establish equilibrium in such a way as to partially counteract the imposed change

Question 19

Effect of changes on equilibrium:

1. Concentration

Answer 19

Favour direction of equation that will oppose change

• decrease = favour side that produces more
• increase = favour side that ‘uses up’

Question 20

Effect of changes on equilibrium:

2. Pressure

Answer 20

Increase = favour side that has less particles
Decrease = favour side with more particles

Question 21

Effect of changes on equilibrium:

3. Temperature

Answer 21

• increase: favour endothermic rxn

- decrease: favour exothermic rxn

Question 22

Effect of changes on equilibrium:

4. Volume

Answer 22

Increase volume = decrease pressure

Decrease volume = increase pressure

Question 23

Effect of changes on equilibrium:

5. Catalyst

Answer 23

No effect on position in equilibrium but allows system to reach equilibrium quicker