Chapter 14: Chemical Equilibria

Question 1

What are the two aspects of chemistry and how do they relate?

Answer 1

Kinetics and thermodynamics.
The faster the reaction (kinetics) the less stable the reaction (thermodynamics)

Question 2

What is chemical equilibrium?

Answer 2

It is a dynamic process where the concentration of products and reactants remain constant over time.
In other words, the rate of the forward reaction equals the rate of the reverse.

Question 3

What is “big K” and what does it equal?

Answer 3

K is the equilibrium constant it equals the rate constant of the forward reaction divided by the rate constant of the reverse reaction. (K = kf/kr). K = [Products]/[Reactants]

Question 4

What is the equilibrium constant expresion?

Answer 4

Ration of equilibrium concentrations or partial pressures of products to reactants, each term raised to a power equal to the coefficient of that substance in a balanced chemical equation
aka mass action expression

Question 5

Mass action expression:

Answer 5

Equivalent to equilibrium constant expression, but applied to reaction mixtures that may or may not be at equilibrium

Question 6

What is the law of mass action?

Answer 6

The principle relating the balanced chemical
equation of a reversible reaction to its mass
action expression (or equilibrium constant
expression)

Question 7

What is the relationship between Kp and Kc?

Answer 7

Kp = Kc (RT)^^n
^n = number moles gaseous products - number of moles of gaseous reactants.
R = Gas constant
T = temperature in K

Question 8

What is the relationship between the K forward and the K reverse?

Answer 8

K forward = 1/K reverse

Question 9

How does the size of K relate with the amount of Products/Reactants made.

Answer 9

Large K favors products
Small K favors reactants
Mediums: comparable amounts of both

Question 10

How is the equilibrium constant related of reaction two related to the K of reaction 1 if reaction two is half of reaction one?

Answer 10

K2 = (K1) ^1/2

Question 11

How is the equilibrium constant related of reaction two related to the K of reaction 1 if reaction 2 is twice reaction 1?

Answer 11

K2 = (K1) ^2

Question 12

How does the relationship of Q and K relate to whether more products or reactants will be produced?

Answer 12

Q < K more products made
Q > K more reactants made
Q = K equilibrium

Question 13

What are the types of equilibrium?

Answer 13

Homogenous: All products/reactants is some physical state
Heterogenous: Products/reactants are in different physical states

Question 14

What physical states change their concentration with respect to time?

Answer 14

Gas concentrations change with respect to time. Pure solid and liquid concentration s do not change with respect to time.

Question 15

What physical states change their concentration with respect to time?

Answer 15

Gas concentrations change with respect to time. Pure solid and liquid concentration s do not change with respect to time.
Kc depends on gas (and aqueous)

Question 16

What is Le Chatelier’s Principle?

Answer 16

When stress is added to a system in equilibrium the reaction shifts to restore equilibrium.

Question 17

How will a reaction shift when pressure is increased verses when pressure is decreased?

Answer 17

When pressure is increased the reaction will shift to the side with smaller volume– less moles of gas and aqueous solution
When pressure is decreased the reaction will shift to the side will the greater volume–more moles of gas and aqueous solutions

Question 18

How will exothermic and endothermic reactions shift when heat is added or taken away?

Answer 18

Exothermic: heat added shift toward reactants, taken away shift toward products
Endothermic: heat added shift toward products, taken away shift toward reactants

Question 19

What is the catalysts effect on equilibrium?

Answer 19

A catalyst will decrease the time it takes to get to equilibrium but it will not affect the concentrations of reactants or products

Question 20

What does RICE stand for? What do RICE tables allow us to do?

Answer 20

1) balanced Reaction 2) Initial contditions 3) Changes in system 4) Equilibrium values

It allows us to calculate eqilibrium concentrations

Question 21

What are the three cases of RICE tables?

Answer 21

1) Kp value is very large (much greater than 1) no assumptions can be made. Quadratic equation is used
2) Kp value is very small (less than 0) we can make an assumptions because very little change has occurred. We say that the x in the denominator equals zero
3) Two moles of both products and reactants involved and the initial concentrations are the same you can take the square roots of both sides of the equation.