DF5 : Catalysis and Cracking Flashcards Preview

OCR B Chem 2: Developing Fuels > DF5 : Catalysis and Cracking > Flashcards

Flashcards in DF5 : Catalysis and Cracking Deck (16)
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1
Q

Are the products of cracking predictable?

A

No, they are normally random, with the same molecule giving different cracking products

2
Q

Without a catalyst, what would the cracking process need?

A

It would require extremely high temperatures and pressures and would take far longer, which would be more expensive

3
Q

What, in short terms, occurs in the catalytic cracking process?

A

A hydrocarbon vapour is passed over a heated solid catalyst

4
Q

What temperature does catalytic cracking take place at?

A

450 - 500 degrees

5
Q

Define “catalyst”

A

A substance that speeds up a chemical reaction but can be recovered chemically

6
Q

Define “catalysis”

A

The process of speeding up a chemical reaction using a catalyst

7
Q

Do catalysts undergo any permanent chemical change during a reaction?

A

No

8
Q

Do catalysts change physically?

A

Yes, they crumble/become roughened

9
Q

What does catalysts changing physically suggest?

A

That they take part somewhat in the reaction, although they can be regenerated

10
Q

How much of a catalyst is usually required?

A

Only small amounts

11
Q

What do catalysts affect in the reaction?

A

Its rate, not the amount of product formed

12
Q

Do catalysts appear as reactants in the overall equation?

A

No

13
Q

Define “homogeneous catalysis”

A

Catalysis involving a reactant and catalyst in the same physical state

14
Q

Give one example of homogeneous catalysis

A

Enzyme catalysed reactions in cells take part in an aqueous solution

15
Q

Define “heterogeneous catalysis”

A

Catalysis where the catalysts and products are in different physical states

16
Q

What does heterogeneous catalysis usually involve?

A

A mixture of gases/liquids in the presence of a solid catalyst, providing a surface for the reaction to take part on