Unit 3.4.2 - Equilibria

Question 1

What is the sign for a reversible reaction?

Answer 1

⇋

Question 2

What happens to the speed of the forward and backward reaction after a reaction has started?

Answer 2

To begin with the forward reaction happens much faster but as the reactants get used up the forward reaction slows down, however as more products are formed the backward reaction begins to speed up, until they both happen at the same rate

Question 3

What is a dynamic equilibrium?

Answer 3

Where the forward and backward reaction are happening at the same rate and the concentrations of the reactants and products isn’t changing

Question 4

What are two conditions for a dynamic equilibrium to be maintained?

Answer 4

Closed system at a constant temperature

Question 5

What does K_c stand for?

Answer 5

The equilibrium constant

Question 6

What is K_c?

Answer 6

A quantitative value for the position of equilibrium at a given temperature

Question 7

What is the general formula for K_c for this equation: aA + bB ⇋ cC + dD ?

Answer 7

Question 8

What does [C] mean?

Answer 8

The concentration of C

Question 9

What three things alter the position of equilibrium in a reversible reaction?

Answer 9

Temperature, pressure and concentrations used

Question 10

Is the forward or backward reaction faster when the position of equilibrium moves to the left?

Answer 10

The backward reaction

Question 11

If the forward reaction is faster which way has the position of equilibrium moved?

Answer 11

To the right

Question 12

If the backward reaction is faster are more products or reactants formed?

Answer 12

Reactants

Question 13

If more reactants are produced which was had the position of equilibrium moved?

Answer 13

To the left

Question 14

If the forward reaction is faster are more products or reactants formed?

Answer 14

Products

Question 15

If more products are formed which was has the position of equilibrium moved?

Answer 15

To the right

Question 16

What is Le Chatelier’s principle?

Answer 16

When a closed system in dynamic equilibrium is disturbed, it responds in such a way as to oppose the change and restore the equilibrium

Question 17

If a reaction is exothermic what happens to the position of equilibrium if you increase the temperature?

Answer 17

The system will seek to oppose the increase in temperature by favouring the endothermic reaction to try and reduce the temperature, this increases the backwards reaction shifting the position of equilibrium to the left and producing more reactants

Question 18

If a reaction is endothermic what happens to the position of equilibrium if you increase the temperature?

Answer 18

The system will seek to oppose the increase in temperature by favouring the endothermic reaction to try and reduce the temperature, this increases the forwards reaction shifting the position of equilibrium to the right and producing more products

Question 19

What affects K_c? And what doesn’t?

Answer 19

Temperature does but pressure and changing concentrations of things doesn’t

Question 20

If by changing the temperature you form more products how does K_c change?

Answer 20

Kc will rise

Question 21

What happens to the position of equilibrium if you increase the concentration of the the reactants in a reaction?

Answer 21

The equilibrium tries to get rid of the extra reactants by favouring the forward reaction shifting the position of equilibrium to the right producing more products

Question 22

What happens to the position of equilibrium if you increase the concentration of the the products in a reaction?

Answer 22

The equilibrium tries to get rid of the extra products by favouring the backward reaction shifting the position of equilibrium to the left producing more reactants

Question 23

If by changing the concentration of the products you form more reactants how does K_c change?

Answer 23

Kc remains unchanged

Question 24

A + B ⇋ C, what happens to the position of equilibrium is you increase the pressure?

Answer 24

The system seeks to oppose the increase in pressure by favouring the side with the fewest moles, increasing the forward reaction and producing more products

Question 25

If by changing the pressure you produce more reactants how does K_c change?

Answer 25

Kc remains unchanged

Question 26

How do catalysts effect the position of equilibrium and K_c?

Answer 26

They have no effect because they increase the forward and backward reactions by the same rate and so the equilibrium position doesn’t move