Catalysts

Question 1

Drawn a general enthalpy profile diagram showing the effect of a catalyst to a reaction.

Answer 1

-A catalyst lowers the activation energy of the reaction by providing an alternative route for the reaction to follow. The alternative route has a lower energy.

Question 2

Why are catalysts benefits to the environment?

Answer 2

With less energy required, less fossil fuel is burnt and less carbon dioxide will be released into the atmosphere during energy production.

Question 3

Why are catalysts a benefit to industrial companies?

Answer 3

In many industrial processes, the catalyst will significantly speed up the process by lowering the activation energy of the reaction. Less energy is then required for the molecules to react. Much of this energy is taken from electricitiy supplies or by burning crude oil. If a process can run using less energy, then this saves energy costs.

Question 4

State the examples of transition metals catalysts in:

• The haber process
• H₂SO₄ production
• hydrogentation of margarine

Answer 4

• Iron is used as a catalyst in the haber process
• V₂O₅ in the contact process within H₂SO₄.
• Ni is used as a catalyst in the hydrogenation of margarine.

Question 5

Why is the production of ammonia of great economic importance?

Answer 5

The ammonia produced is used as the basis of fertiliser manufacture, improving crop yields to feed the ever-increasing world population.

Question 6

Write the reaction for the production of ammonia.

Answer 6

N₂(g)+3H₂(g) ⇔ 2NH₃(g)

Question 7

Explain how the use of iron helps catalyse the production of ammonia.

Answer 7

The triple bond in nitrogen has to be broken. This requires a large input of energy, contributing to a high activation energy. Iron is used to catalyse this reaction, weakening the nitrogen to nitrogen trible bond and lowering the activation energy.

Question 8

Define heterogeneous catalysis

Answer 8

Heterogeneous catalysis is a catalysis of a reaction in which the catalyst has a different physical state from the reactants; frequently, reactants are gases whilst the catalyst is a solid.

Question 9

Homogeneous catalysis

Answer 9

Is catalysis of a reaction in which the catalyst and reactants are in the same physical state, which is most frequently the aqueous or gaseous state.

Question 10

What is biocatalysis?

Answer 10

Biocatalysis is any process in which the catalyst is an enzyme.

Question 11

What is specificity?

Answer 11

Something that can be explained by considering the structure of an enzyme and the molecule being catalysed - known as the substrate. The lock-and-key mechanism for enzyme action explains how the substrate relies on the enzyme being the perfect fit.

Question 12

What are enzymes?

Answer 12

Enzymes are large protein molecules,able to catalyse the reactions of large quantities of biological molecules in very short periods of time.

Question 13

What conditons to most enzymes generally operate at?

Answer 13

Enzymes operate under mild conditions, such as low temperatures, atmoshperic pressure and at an optimum pH value.

Question 14

What are all the benefits from using enzymes in industry ?

Answer 14

• Lower temperatures and pressures can be used than with conventional organic catalysts, saving energy and costs.
• Enzymes often allow a reaction to take place which forms pure products, with no side reactions. They often remove the need for complex seperation techniques,thereby reducing costs.
• Conventional catalysts are often poisonous and can pose disposal problems at the end of their industrial life. Enzymes are biodegradable.

Question 15

What are the advantages of using enzymes in washing powders?

Answer 15

The use of enzymes in washing powders and detergents reduces the temperature required for washing. Milder conditions can be used, causing less damage to the clothes being washed.