Section 2: Equilibrium

Question 1

What is a dynamic equilibrium?

Answer 1

The forward and reverse reactions are going at the same rate and there’s no overall change in the concentrations of the reactants and products.

Question 2

In what system can a dynamic equilibrium occur?

Answer 2

Closed system (a system where nothing can get in or out) at a constant temperature.

Question 3

In which systems can equilibria be set up?

Answer 3

Physical system - changes physical stage

Chemical system - when the moles of the reactants change until equilibrium is reached

Question 4

What is the equilibrium constant equation?

Answer 4

Kc = [D]d [E]e / [A]a [B]b

Question 5

What is a homogenous reaction?

Answer 5

All products and reactants are in the same stages, e.g. Gases

Question 6

What is a heterogenous equation?

Answer 6

Reactants and products are in different states

Question 7

What is the rules for calculating kc for heterogeneous equations?

Answer 7

If the mixture is heterogeneous only gases and aqueous substances go into the expression for the equilibrium constant (any solids or liquids get left out)

Question 8

What is partial pressure?

Answer 8

In a mixture, each individual has exerts its own pressure

Question 9

How do you calculate total pressure?

Answer 9

By adding all the partial pressures up

Question 10

How to calculate partial pressure of a gas in a mixture?

Answer 10

Mole fraction of gas x total pressure of the mixture

Question 11

How to calculate mole fraction of a gas in a mixture?

Answer 11

Number of moles of gas / total number of moles of gas in the mixture

Question 12

When is the GAS equilibrium Kp used?

Answer 12

Reversible reaction where some or all of the reactants and products are gases

Question 13

What is the equation for Kp?

Answer 13

Kp = p(D)d p(E)e / p(A)a p(B)b

Question 14

How to use Kp for heterogeneous equilibria?

Answer 14

Don’t include solids or liquids into the expression

Question 15

What is Le Chatelier’s Principle?

Answer 15

If there’s a change in concentration, pressure or temperature, the equilibrium will move to help counteract the change

Question 16

What happens if the position of the equilibrium moves to the left?

Answer 16

You’ll get more reactants

Question 17

What happens if the position of the equilibrium moves to the right?

Answer 17

You’ll get more products

Question 18

What affects the value of Kc?

Answer 18

Temperature

Question 19

What happens to the equilibrium if you increase the temperature?

Answer 19

The equilibrium shifts in the endothermic direction (positive H) to absorb the heat.

Question 20

What happens to the equilibrium is you decrease the temperature?

Answer 20

The equilibrium shifts in the exothermic direction (negative H) direction to try to replace the heat.

Question 21

How does more product formed affect Kc?

Answer 21

Increases KC

Question 22

How does less product formed affect Kc?

Answer 22

Will decrease

Question 23

How does concentration affect Kc?

Answer 23

It doesn’t. Thus the reaction needs to change the concentrations in order to keep Kc the same

Question 24

How is the value of Kp affected by change in pressure?

Answer 24

Increasing pressure shifts the equilibrium to the side with fewer gas molecules to reduce pressure

Decreasing pressure shifts the equilibrium to the side with more gas molecules. This raises the pressure again.

Question 25

How do catalysts affect the rate of Kp/Kc ?

Answer 25

They have no effect. This is because a catalyst will increase the rate of both the forward and backward reactions by the same amount.