Fractional distillation of crude oil

Question 0

Define saturated

Answer 0

Contain single carbon-carbon bonds only

Question 1

Define a hydrocarbon

Answer 1

A compound consisting of hydrogen and carbon only

Question 2

Define unsaturated

Answer 2

Contain a C=C double bond

Question 3

Define molecular formula

Answer 3

The formula which shows the actual number of each type of atom

Question 4

Define the Empirical formula

Answer 4

The formula shows the simplest whole number ratio of atoms of each element in the compound

Question 5

What does petroleum mainly consist of?

Answer 5

A mixture of alkane hydrocarbons

Question 6

List the main stages of fractional distillation.

Answer 6

• Oil is pre-heated
• then passed into column.
• The fractions condense at different heights
• The temperature of column decreases upwards
• The separation depends on boiling point.
• Boiling point depends on size of molecules.
• The larger the molecule the larger the van der waals forces
• Similar molecules (size, bp, mass) condense together
• Small molecules condense at the top at lower temperatures
• and big molecules condense at the bottom at higher temperatures.

Question 7

Define Cracking

Answer 7

Conversion of large hydrocarbons to smaller hydrocarbon molecules by breakage of C-C bonds

Question 8

Name 3 economic reasons for cracking

Answer 8

1- the petroleum fractions with shorter C chains (e.g. petrol) are in more demand than larger fractions

2- to make use of excess larger hydrocarbons and to supply demand for shorter ones, longer hydrocarbons are cracked

3- the products of cracking are more valuable than the starting materials (e.g. ethene used to make poly(ethene))

Question 9

This chemical process involves the splitting of which type of bond?

Answer 9

Strong covalent

Question 10

Does cracking require high or low temperatures?

Answer 10

High temperatures

Question 11

What are the two main types of cracking?

Answer 11

Thermal and catalytic

Question 12

In thermal cracking what pressure is required?

Answer 12

A high pressure of 7000 kPa

Question 13

In thermal cracking what temperature is required?

Answer 13

A high temperature of 400-900 degrees Celsius

Question 14

What does thermal cracking produce mostly?

Answer 14

Alkenes - e.g. Ethene is used for making polymers and ethanol

Question 15

What does thermal cracking sometimes produce?

Answer 15

Hydrogen - this is used in the Haber Process

Question 16

In catalytic cracking what pressure is required?

Answer 16

Low pressure

Question 17

In catalytic cracking what temperature is required?

Answer 17

A high temperature of 450 degrees Celsius

Question 18

In catalytic cracking what type of catalyst is used?

Answer 18

Zeolite

Question 19

What does catalytic cracking produce?

Answer 19

Branched and cyclic alkanes and aromatic hydrocarbons

Question 20

Which is cheaper, catalytic or thermal cracking?

Answer 20

Catalytic is cheaper than thermal cracking because it saves energy as lower temperatures and pressures are used

Question 21

Do branched and cyclic hydrocarbons burn more or less cleanly?

Answer 21

They burn more cleanly and are used to give fuels a higher octane number