Organic Chemistry

Question 1

What is crude oil made from?

Answer 1

Different length Hydrocarbons

Question 2

List four alkanes.

Answer 2

Methane, Ethane, Propane, Butane

Question 3

‘draw’ (imagine) the following alkanes:
a). C2H6 b). C4H10

Answer 3

H H H H H H
H — C —C —H H - C— C — C — C - H
H H H H H H

Question 4

What is the formula for alkanes?

Answer 4

Cn + H2n +2

Question 5

Describe how crude oil is made.

Answer 5

From the remains of dead plankton and other animals and plants that fall to the bottom of the sea and get covered in layers of mud and other substances.

Question 6

What is the combustion equation?

Answer 6

Hydrocarbon + Oxygen —> Carbon
dioxide +
water

Question 7

What are the uses of crude oil?

Answer 7

Fuel for transport e.g. petrol and diesel.
Used to make other compounds such as polymers, lubricants, solvents, detergents

Question 8

Describe the process of fractional distillation.

Answer 8

Crude oil is a mixture of hydrocarbons and they are heated to form a gas. They all have different boiling points so separate out at different temperatures. Long chain hydrocarbons have high boiling points, short chain molecules have low boiling points.

Question 9

How does the length of the hydrocarbon affect the boiling point?

Answer 9

The longer the hydrocarbon the higher the boiling point - more energy is needed to break up the molecules

Question 10

What is bromine water a test for?
What colour does it go and what is the original colour?

Answer 10

Alkene
Goes from orange to colourless

Question 11

Describe alkanes.

Answer 11

Alkanes are saturated (no C=C double bond) so they contain as many hydrogen atoms as possible

Question 12

Describe alkenes.

Answer 12

Alkenes are unsaturated so we could add more hydrogen atoms to them

Question 13

What are the products of incomplete combustion and what are the problems with these?

Answer 13

1: Carbon monoxide
Problem: Poisonous gas, binds to our haemoglobin instead of oxygen

2: Carbon (soot)
Problem: causes respiratory diseases if breathed in

Question 14

Describe cracking.

Answer 14

Cracking is a type of thermal decomposition. A long chain alkane is broken into one shorter alkane and one or more alkene.

Question 15

What is the point of cracking?

Answer 15

Long alkanes aren’t very useful (they don’t burn well and can’t make consumer products from them) so they get turned into more useful compounds:
Short alkanes are better fuels
Alkenes can be used to make plastics

Question 16

What is cracking?

Answer 16

The breaking down of large chain hydrocarbons into shorter chains.

Question 17

Draw (imagine) a diagram for an alkene.

Answer 17

H H
C=C
H H

Question 18

What is the formula for alkenes?

Answer 18

C2H2n

Question 19

What are the two methods of cracking?
Describe them.

Answer 19

Steam - heated in vapour, mixed with steam, heated at very high temperature
Catalytic - heated into a gas, passed over aluminium oxide catalyst, molecules split

Question 20

What are hydrocarbons?

Answer 20

Molecules made from only hydrogen and carbon atoms

Question 21

Describe the properties of a larger hydrocarbon.

Answer 21

• More viscous
• High boiling point
• Less volatile
• Less flammable