Chapter 4B - Catalysts

Question 1

What is a catalyst?

Answer 1

Any substance that causes a reaction to proceed faster/slower without being consumed itself.

Question 2

What does a catalyst provide?

Answer 2

An alternative reaction pathway that has a lower activation energy

Question 3

How does a Catalyst work?

Answer 3

• Binds with reactant particles, weakening the bonds within the reactants
• decreases the amount of energy required to break bonds
• greater proportion of collisions have energies > EA

Question 4

add percentage yield

What is the effect of a catalyst?

Answer 4

• lowers the EA for both the forwards & reverse reaction by the same amount
• The percentage yield remains unchanged
• Does not affect the enthalpy change

Question 5

What are some common forms of catalysts?

Answer 5

Generally solid form
* porous (gauze)
* powdered (increase SA)
* pure or compounds of transition metals

Question 6

What is an advantage of using a catalyst?

Answer 6

Can be used in a variety of reactions, unlike enzymes which are specific

Question 7

What are the types of catalysts?

Answer 7

1. Heterogenous
2. Homogenous

Question 8

Define Homogenous

Answer 8

Catalyst is in the same physical state as the reactants and products

Question 9

Define Heterogenous

Answer 9

Catalyst is in a different physical state compared to the reactants and products (most common)

Question 10

Why do we use solid catalysts in guaze/powdered forms?

Answer 10

• rely on reactant molecules absorbing onto the catalyst surface
• forms maximise the surface area
• improves catalyst efficiency