Chemical Equilibrium

Question 1

What is dynamic equilibrium?

Answer 1

The condition where the rate of the forward reaction equals the rate of the reverse reaction

Question 2

Are the concentrations of reactions and products equal at equilibrium?

Answer 2

No the rate is

Question 3

What is the formula for the equilibrium constant?

Answer 3

aA + bB —> cC + dD

K= [C]^c[D]^d/[A]^a[B]^b

Concentration of products raised to coefficient in balanced equation divided by concentration of reactants raised to coeffficient

Question 4

What is true of the equilibrium constant?

Answer 4

Applies to system at equilibrium, ratio of products to reactants, concentration is raised to equivalent stoichiometric coefficient

Question 5

What is the law of mass action?

Answer 5

Relationship between a balanced chemical equation and K

Question 6

How can you express K?

Answer 6

Kc (concentration)

Kp (pressure)

Question 7

How can you relate Kc and Kp?

Answer 7

Kc= Kp(1/RT)^deltan

Kp= Kc(RT)^deltan

Question 8

What is delta n?

Answer 8

Change in moles from products to reactant

Find the stoichiometric difference of gases

Question 9

For what value does Kc equal Kp?

Answer 9

Delta n is 0

Question 10

What is activity?

Answer 10

A measure of deviation from the standard state

Question 11

What is a large K indicate?

Answer 11

K > 1

Numerator is greater than denominator so the amount of products is favored over reactants

Reaction lies to the right

Question 12

What does a small K indicate?

Answer 12

K < 1

Numerator smaller than denominator so the amount of reactants is favoured over reactants

reaction lies to the left

Question 13

What does a K that is approx 1 mean?

Answer 13

neither direction is favoured

reaction proceeds about halfway to completion

Question 14

If you reverse a chemical equation how can you find the equilibrium constant given K of the reaction before it was reversed?

Answer 14

1 divided by the equilibrium constant of the reaction before it was reversed

Question 15

If you multiply an equation by “n” hpw does the original K change?

Answer 15

raise every concentration to “n”

multiply K by “n”

Question 16

If you are adding together two equations to get the final equation, how can you find the K values given K of the original?

Answer 16

multiply them together

Question 17

What are ICE tables used for? What does ICE stand for?

Answer 17

to find the equilibrium concentration in order to find K

Initial, change, equilibrium

Question 18

What is Q?

Answer 18

the reaction quotient

measures the relative amounts of products and reactants present during a reaction at a particular point in time (measures progress towards equilibrium)

Question 19

What does the reaction quotient do?

Answer 19

predicts the direction of change (if we know K)

always approaches equilibirum as the final state

Question 20

What does it mean if Q < K?

Answer 20

reaction proceeds to the right, products need to be formed to reach equilibrium

Question 21

What does it mean if Q > K?

Answer 21

reaction proceeds to the left, reactants need to be formed to reach equilibrium

Question 22

What does it mean if Q = K?

Answer 22

equilibrium has been reached

Question 23

How can you find the equilibrium amounts when you know K and all but one amount of reactant/product?

Answer 23

1. write the expression for K
2. rearrange formula to isolate unknown
3. plug in values and solve

Question 24

How can you find the equilibrium amounts when you know K and all of the initial amounts?

Answer 24

1. using balanced chemical equations, create an ICE table
2. use initial amounts to calculate Q and figure out the direction the reaction will proceed
3. for the C row, represent the change with x, + or - depending on direction, and include coefficients
4. add up columns to get E row
5. sub into K formula and solve

Question 25

How can you simplify equilibrium problems?

Answer 25

careful inspection of K and initial amounts

a large amount of initial reactant and a small K can mean that the equilibrium concentration may be essentially unchanged

Question 26

What is Le Chatelier principle?

Answer 26

When a chemical system at equilibrium is disturbed, the system shifts in a direction that minimizes the disturbance.

Question 27

How can you disturb a chemical system at equilibrium?

Answer 27

1. change the amount of product
2. change the amount of reactant
3. change the reaction volume
4. change the reaction pressure
5. change the reaction temperature

Question 28

What is true when add/remove reactant?

Answer 28

increasing the amount of reactant (Q<K) causes a shift to the right

Decreasing the amount of reactant (Q>K) causes a
shift to the left

Question 29

What true when you add/remove product?

Answer 29

Increasing the amount of product (Q>K) causes a shift to the left

Decreasing the amount of product (Q<K) causes a shift to the right

Question 30

What is true when you increase/decrease the volume?

Answer 30

Increasing the volume causes a shift in the direction that has more moles of gas

Decreasing the volume causes a shift in the direction that has fewer moles of gas

Question 31

What is true when you increase/decrease the pressure?

Answer 31

Increasing the pressure causes a shift in the direction that has fewer moles of gas

Decreasing the pressure causes a shift in the direction that has more moles of gas

Question 32

What is true when you increase/decrease the temperature for exothermic reactions?

Answer 32

Increasing the temperature causes exothermic reactions to shift left and decreases K

Decreasing the temperature causes exothermic reactions to to shift right and increases K

Question 33

What is true when you increase/decrease the temperature for endothermic reactions?

Answer 33

Increasing the temperature causes endothermic reactions to shift right and increases K

Decreasing the temperature causes endothermic reactions to shift left and decreases K