Equilibrium Key Terms and Processes

Question 1

Dynamic Equilibrium

Answer 1

the rate of the forwards reaction is equal to the rate of the backwards reaction, and the concentrations of the reactants and products do not change

Question 2

Le Chatelier’s Principle

Answer 2

When a system in equilibrium is subjected to an external change, the system readjusts itself to minimise the effect of that change

Question 3

Effect of temperature when the forwards reaction is exothermic (-ve ΔH)

Answer 3

Increased temperature;
Position of equilibrium moves to the LHS; more reactants are made
Decreased temperature;
Position of the equilibrium shifts to the RHS, more products are made

Question 4

Effect of temperature when the forwards reaction is endothermic (+ve ΔH)

Answer 4

Increased temperature;
Position of the equilibrium moves to the RHS, more products are made
Decreased temperature;
Position of the equilibrium moves to the LHS, more reactants are made

Question 5

Effect of pressure on a system

Answer 5

Increasing the pressure of the system will shift the position of the equilibrium to the side where the lowest volume of moles are created.
Decreasing the pressure of the system will shift the position of the equilibrium to the side where the most volume of moles are created

Question 6

The effect of a catalyst on equilibrium

Answer 6

A catalyst has no effect on the the position of the equilibrium, it simply speeds up the rates of the forwards and backwards reaction. It increases the rate at which equilibrium is reached.

Question 7

In Kc calculations , square brackets are representative of…?

Answer 7

Concentration

Question 8

The Equilibrium law/Kc equation

Answer 8

[reactants]

Question 9

Kc = 1 ?

Answer 9

position of equilibrium between

Question 10

Kc > 1 ?

Answer 10

Position of equilibrium is towards the products

Question 11

Kc < 1 ?

Answer 11

Position of equilibrium is towards the reactants

Question 12

Homogeneous Equilibria

Answer 12

Contains equilibrium species that all have the same state or phase.

Question 13

Heterogeneous Equilibria

Answer 13

Contains equilibrium species that have different states or phases.

Question 14

Mole Fraction

Answer 14

The mole fraction of a gas is the same as its proportion by volume to the total volume of gases in a gas mixture

Question 15

Partial Pressure

Answer 15

partial pressure =

mole fraction x total pressure

Question 16

K = 100

Answer 16

indicates an equilibrium well in favour of the products

Question 17

K = 1 x 10^-2

Answer 17

indictates an equilibrium well in favour of the reactants

Question 18

At a set temperature Kc is..?

Answer 18

..constant and does not change despite any modifications to concentration, pressure or the presence of a catalyst.

Question 19

When temperature is changed, Kc..?

Answer 19

Kc also changes, it is the only variable that will change the value of Kc

Question 20

If the forwards reaction is exothermic and the temperature is raised, the equilibrium constant …

Answer 20

… decreases with increasing temperature, raising the temperature decreases the equilibrium yield of products, which means in the Kc equation the numerator will get smaller, while the denominator will get larger, which makes Kc smaller

Question 21

If the forwards reaction is endothermic and the temperature is raised, the equilibrium constant…

Answer 21

…increases with increasing temperature, raising the temperature increases the equilibrium yield of products, which means that in the Kc equation the numerator will get larger, while the denominator will get smaller, which makes Kc larger

Question 22

How do temperature and pressure affect equilibrium constants?

Answer 22

The value of an equilibrium constant Kc is seemingly unaffected by by changes in concentration and pressure