2.5 - Basic organic chemistry

Question 1

What are fractions?

Answer 1

Molecules that have similar boiling points

Question 2

What is a hydrocarbon?

Answer 2

A molecule that only contains hydrogen and carbon

Question 3

What is an alkane?

Answer 3

A hydrocarbon that only has a single bond between the carbon atoms

Question 4

Why are alkanes known as being saturated?

Answer 4

Because they can’t have any more hydrogen atoms added to the carbon atoms

Question 5

What are short chain alkanes used for?

Answer 5

For fuels and combustion

Question 6

Why do long chain alkanes have to be cracked?

Answer 6

To break the alkanes into shorter chains and into alkenes

Question 7

How is crude oil separated into fractions?

Answer 7

Oil is heated and pumped into the bottom of a fractionating column where it vaporizes. As the vapourized oil rises it cools and condenses. The heavy fractions have high boiling points and condense near the bottom of the column

Question 8

How to remember how many carbon atoms there are in each alkane

Answer 8

1. M - methane
2. E - ethane
3. P - protane
4. B - butane
5. P - pentane
6. H - hexane

Question 9

What are alkenes

Answer 9

Hydrocarbons that contain at least one double covalent bond between the carbon atoms

Question 10

Why are alkenes unsaturated hydrocarbons?

Answer 10

Because they contain at least one double covalent bond between carbon atoms

Question 11

How to distinguish between saturated and unsaturated compounds?

Answer 11

• add red bromine water

- red colour disappears in the presence of unsaturated compounds (alkenes)

Question 12

What is cracking?

Answer 12

The process of breaking down large hydrocarbons into smaller ones

Question 13

How do we crack alkanes?

Answer 13

By heating a large chain alkane and putting it over a hot catalyst

Question 14

Why do we crack alkanes?

Answer 14

Because large chain alkanes are less useful and are not in demand

Question 15

C2H4 + BR2 = (addition reaction)

Answer 15

C2H4BR2

Question 16

Equation for complete combustion

Answer 16

Fuel + O2 = CO2 + H20

Question 17

Equation for incomplete combustion

Answer 17

Fuel + O2 = CO + H20

Question 18

What happens when you crack an alkene?

Answer 18

Polymerisation - polymers

Question 19

Why are alkenes very reactive?

Answer 19

Because they have a double bond

Question 20

What is addition polymerisation?

Answer 20

The process by which alkenes are joined together

Question 21

What does addition polymerisation involve?

Answer 21

The reaction of many unsaturated monomers to form a saturated polymer

Question 22

What is a condensation polymer?

Answer 22

Made from two or more different monomers

Question 23

What are thermoplastics?

Answer 23

Plastics that soften when heated e.g plastic bags, home containers

Question 24

Why can thermoplastics be reshaped?

Answer 24

The forces are so weak so the chains can slide past each-other
They have no cross links
E.g polythene, PVC

Question 25

What are thermosets?

Answer 25

Plastics that are resistant to heat e.g saucepan handles

Question 26

Why are thermosets resistant to heat?

Answer 26

They have strong cross linkages so the chains can’t move past eachother

Question 27

How to test for a thermosetting or softening plastic?

Answer 27

Heat them in a bunsen
If it softens, thermoplastic
Char and black = thermoset

Question 28

What are saturated hydrocarbons?

Answer 28

Where the compound only contains single covalent bonds between the carbon atoms

Question 29

What are unsaturated hydrocarbons? (Alkenes)

Answer 29

Where the compound contains at least one double covalent bond between carbon atoms

Question 30

Use of polythene, polypropene, PTFE, PVC

Answer 30

• plastic bags and bottles
• polypropene = buckets and crates
• PTFE = non-stick coating for pans, containers
• PVC = pipes and vinyl flooring