Chapter 6 (Equilibria)

Question 1

What state do reversible reactions reach?

Answer 1

A dynamic equilibrium

Question 2

What are the two features of a dynamic equilibrium?

Answer 2

• Forward and backward reactions occur at equal rates.

* The concentrations of reactants and products remain constant.

Question 3

What does Le Chatelier’s principle state?

Answer 3

If an external condition changes then the equilibrium will shift to oppose the change.

Question 4

What is the effect on equilibrium if temperature is increased?

Answer 4

The equilibrium will move in the endothermic direction to try to reduce the temperature by absorbing heat.

Question 5

What is the effect on equilibrium if temperature is decreased?

Answer 5

The equilibrium will move in the endothermic direction to increase the temperature by releasing heat.

Question 6

What is the effect on equilibrium if pressure is increased?

Answer 6

Equilibrium will shift towards the side with fewer moles of gas to oppose the change and decrease pressure.

Question 7

What is the effect on equilibrium if pressure is decreased?

Answer 7

Equilibrium will shift towards the side with more moles of gas to oppose the change and increase the pressure.

Question 8

What are the advantages and disadvantages of changing temperature?

Answer 8

Lower temperature may increase the yield but reaction may be slower.

Increasing temperature may be more expensive/require more energy.

Question 9

What are the advantages and disadvantages of changing pressure?

Answer 9

Increasing pressure may give a higher yield and a faster rate of reaction but conditions may be expensive to produce and the stronger equipment to contain higher pressure may be expensive.

Question 10

What is the effect on equilibrium if concentration is increased?

Answer 10

Equilibrium will shift away from the side with the increased concentration to oppose the change and decrease the concentration.

Question 11

What is the effect on equilibrium if concentration is decreased?

Answer 11

Equilibrium will shift towards the side with the decreased concentration to oppose the change and increase the concentration.

Question 12

What is the effect on equilibrium if a catalyst is added?

Answer 12

No effect on the position of the equilibrium but will increase the rate that equilibrium is reached.

(Will lower the activation energy so lower energy costs)

Question 13

What is the equation for producing ethanol from the hydration of ethene?

Answer 13

CH2=CH2 (g) + H2O (g) ⇌ CH3CH2OH(l)

Question 14

What are the conditions for the production of methanol from the hydration of ethene and why are these conditions used?

Answer 14

Temperature = 300º
Pressure = 70 atm
Catalyst = Concentrated H3PO4

Low temperature gives a good yield but a slow rate

High pressure gives a high yield and a high rate. Too high a pressure would lead to high energy cost for pumps to produce the pressure. High pressure also leads to unwanted polymerisation of ethene to poly(ethene).

Question 15

Define carbon neutral

Answer 15

An activity that has no net annual carbon emissions to the atmosphere.

Question 16

What is the equation for the production of methanol from CO?

Answer 16

CO(g) + 2H2(g) ⇌ CH3OH(g)

Question 17

What are the conditions for the production of methanol from the Carbon Monoxide and why are these conditions used?

Answer 17

Temperature = 400º
Pressure = 50 atm
Catalyst = Chromium and Zinc Oxide

Low temperature gives good yield but slow rate.

High pressure gives a good yield and high rate. Too high pressure would lead to too high energy costs for pumps to produce the pressure.

Question 18

What is the equation for the Haber Process?

Answer 18

N2 + 3H2 ⇌ 2NH3

Question 19

What are the conditions for the Haber Process and why are these used?

Answer 19

Temperature = 450º
Pressure = 200 - 1000atm
Catalyst = Iron

Low temperature gives good yield but slow rate.

High pressure gives a good yield and high rate. Too high pressure would lead to too high energy costs for pumps to produce the pressure.

Question 20

What are the two equations that lead to the production of Sulphur Trioxide?

Answer 20

1) S(s) + O2(g) > SO2(g)

2) SO2(g) + 1/2O2(g) ⇌ SO3(g)

Question 21

What are the conditions for the production of Sulphur Trioxide and why are they used?

Answer 21

Temperature = 450º
Pressure = 1 or 2 atm
Catalyst = V2O5

Low temp gives good yield but slow rate: compromise moderate temp used

High pressure only gives slightly better yield and high rate: too high a pressure would lead to too high energy costs for pumps to produce the pressure

Question 22

Which factor changes Kc?

Answer 22

Temperature

Question 23

What can Kc show?

Answer 23

The larger the Kc then the greater the amount of products, the smaller the Kc then the reactants are favoured.