3.1.6- Equilibria

Question 1

Define dynamic equilibria

Answer 1

Both forward and backward reaction occurring at same time

Question 2

4 features of dynamic equilibrium

Answer 2

• Both reactant and products are present at all time
• The equilibria can be approached from either side
• Reaction is dynamic moving backward and forward
• concentration of reactants and products remain constant

Question 3

What is homogenous

Answer 3

Reactant and products are in the same phase

Question 4

What heterogeneous

Answer 4

Reactants and products are in different phases

Question 5

What is le Chanteliers principle

Answer 5

When a change is applied to a system in dynamic equilibria, the system reacts in such a way as to oppose the effect of the change

Question 6

What happens if the concentration is changed in a reversible reaction

Answer 6

• Kc will not be affected

- Equilibria will move opposite way to where it has been added

Question 7

Example of changing concentration in a reversible reaction

Answer 7

A+2B = C +D

Add more A

The equilibria will move to the right to oppose the change

Question 8

What happens when you change pressure in a reversible reaction

Answer 8

Increase - move to side with fewer gaseous molecules

Decrease - move to side more gaseous molecules

Question 9

What happens when temperature is altered in a reversible reaction

Answer 9

Kc moves to produce a new constant

Question 10

What happens when you increase the temperature of a reversible reaction

Answer 10

Exothermic moves to left

Endothermic moves to right

Question 11

What happens when temperature is decreased in reversible reaction

Answer 11

Exothermic moves to right

Endothermic moves to left

Question 12

If temperature is increased explanation in reversible reaction

Answer 12

Move in endothermic direction to absorb heat

Question 13

If temperature is decreases explaination

Answer 13

Move in exothermic to give out heat to surroundings

Question 14

How does a catalyst affect reversible reactions

Answer 14

Does not affect Kc

Reach equilibria quicker because catalyst increase the forward and backward reaction rates equally

Question 15

What are two industrial processes with reversible reactions

Answer 15

The Haber process

The contact process

Question 16

Explain temperate used in the haber process

Answer 16

450
I.e. A moderate temperature

Adv+ increases the rate of reaction and within working range of catalyst

Dis- lower yield because prefers lower temperature and energy costs

Question 17

Explain pressure used in haber process

Answer 17

20 MPa
I.e. High pressure

Adv+ increase the rate and increases the yield. High pressure is favoured

Dis- energy costs and plant costs

Question 18

Explain the use of catalyst in the haber process

Answer 18

Adv+ increases rate and lowers temperature to be used

Dis- cost and recovery and deactivation of catalyst

Question 19

What are additional conditions of the haber process

Answer 19

Remove NH3 as it is formed
Cool mixture down NH3 forms first
Recycle unused gases

Question 20

Uses of NH3

Answer 20

Fertiliser
Medicine
Explosives

Question 21

What is the equation for the contact process

Answer 21

2SO2 + O2 = 2SO3

Question 22

Explain temperature used in contact process

Answer 22

Moderate temperature

Adv+ increases rate of reaction and in range of catalyst

Dis - lowers yield as prefers lower temperature and energy costs

Question 23

Explain pressure in the contact process

Answer 23

High pressure 200KPa

Adv+ increases the rate of reaction and increases yield high pressure is favoured

Dis- energy costs and plant costs

Question 24

Explain catalyst used in contact process

Answer 24

V2O5 (vanadium pentoxide)

Adv+ increases rate and lower temperature needed

Dis - Catalysts are expensive

Question 25

Show how to calculate Kc from this equation

aA+bB = cC+dD

Answer 25

[A]a[B]b

Question 26

What is Kc not affected by

Answer 26

A change in concentration
A change in pressure
Adding a catalyst

Question 27

What is Kc changed by

Answer 27

A change in temperature