Kinetics

Question 1

What are the requirements for a reaction to take place?

Answer 1

Collision must occur between particles, reactants must possess the activation energy, particles must be oriented in the correct way

Question 2

What effect will pressure change have on position of an equilibrium if the number of moles of reactants is equal to the number of moles of products?

Answer 2

Pressure change will have no effect on equilibrium

Question 3

Does the equilibrium of a reaction depend on total pressure or partial pressures of reaction components?

Answer 3

The equilibrium of reactants and products do not depend on total pressure but on partial pressures of their reaction components

Question 4

What are the 2 ways of changing total pressure of a reaction?

Answer 4

1. By changing the volume of the system
2. By adding an inert gas at constant volume

Question 5

Does changing the total pressure by changing the volume of the system affect equilibrium position?

Answer 5

Yes as this changes the partial pressures of the products and reactants

Question 6

Which of the 2 ways of changing total pressure of a reaction affects equilibrium position?

Answer 6

Changing the total pressure by changing the volume of the system

Question 7

Does changing the total pressure by adding an inert gas at constant volume affect equilibrium position?

Answer 7

No

Question 8

What catalysts (including their symbol) are used in the Haber Process?

Answer 8

Iron (Fe) and molybdenum (Mo)

Question 9

What are the conditions for the Haber Process and why?

Answer 9

• 400-450^C
• 200 atm
• Iron catalyst

The best economic compromise was for the temperature to be about 450°C and pressure of 200 atm, which will give a 30% yield of ammonia. The temperature is low enough for a reasonable yield but high enough for a fast reaction and the pressure is low enough to not need expensive reinforcement apparatus but high enough to give a reasonable yield

Question 10

What’s the Haber process?

Answer 10

It is an artificial nitrogen fixation process and is the main industrial agricultural ammonia production method used today. It is also used for synthetic fibres and explosives.

Question 11

What are the conditions for Ethanol production by hydration and what yield of ethanol does this produce?

Answer 11

• 300^C
• 60-70 atm
• Phosphoric (V) acid catalyst
• Using an ethene: steam ratio of 1: 0.6
  This produces an ethanol yield of around 5% so the unreacted ethene is separated from the reaction mixture and recycled over the catalyst again until a 95% conversion is obtained

Question 12

Why can’t the pressure for Hydration for Ethanol be too high and is this good or bad in terms of Le Chatelier’s principle?

Answer 12

High pressure can cause ethene to polymerise to polyethene which is bad in terms of Le Chatelier’s principle because more pressure means equilibrium would move to oppose the increase in pressure by moving to the right, increasing ethanol yield

Question 13

Why can’t too much steam be used for Hydration for Ethanol and is this good or bad in terms of Le Chatelier’s principle?

Answer 13

Too much steam will dilute the catalyst which is bad in terms of Le Chatelier’s principle because more steam means more reactants so equilibrium would move to oppose the increase in reactant concentration by moving to the right, increasing ethanol yield

Question 14

Le Chatelier’s principle will tell us that to favour the production of ethanol by hydration, we should…?

Answer 14

• Increase the pressure
• Lower the temperature
• Increasing either of the reactants should drive the reaction forward as well, but steam is cheaper

Question 15

What is methanol used for?

Answer 15

Used:
- As a precursor to other commodity chemicals
- In making plastics and bakelite

Question 16

How is methanol produced?

Answer 16

Methanol is produced by the hydrogenation of carbon monoxide, with a mixture of copper and zinc oxides as a catalyst in an exothermic reaction:

CO + 3H2 ↔ CH 3OH

Question 17

Le Chatelier’s principle will tell us that to favour the production of methanol, we should…?

Answer 17

• Increase the pressure
• Lower the temperature

Question 18

What are the conditions for methanol production by hydrogenation?

Answer 18

• 50–100 atm
• 250 °C

Question 19

What does it mean if Kc is equal to 1?

Answer 19

This means that the reaction will reach equilibrium as an intermediate mixture, meaning the amounts of products and reactants will be about the same

Question 20

What Kc value means that the reaction will reach equilibrium as an intermediate mixture, meaning the amounts of products and reactants will be about the same

Answer 20

When Kc = 1

Question 21

What does it mean if Kc is more than 1?

Answer 21

This means that the mixture contains mostly products

Question 22

What Kc value means that the mixture contains mostly products?

Answer 22

When Kc is more than 1

Question 23

What does it mean if Kc is less than 1?

Answer 23

This means that the mixture contains mostly reactants

Question 24

What Kc value means that the mixture contains mostly reactants?

Answer 24

When Kc is less than 1

Question 25

Platinum acts as a heterogeneous catalyst in the reaction between ammonia and oxygen. It provides an alternative reaction route with a lower activation energy.
Describe the stages of this alternative route

Answer 25

• Reactant(s) adsorbed onto the (platinum surface) / (platinum) which provides a surface / active sites
• Reaction (on the surface) or bond breaking(weakening) / bond making occurs (on the surface)
• Desorption (of the product)

Question 26

When ammonia reacts with oxygen, nitrous oxide (N2O) can be produced instead of NO. Give an equation for this reaction

Answer 26

2NH3 + 2O2 → N2O + 3H2O