Organic Part 1, 2 and 3

Question 1

4.1 Hydrocarbons

Answer 1

Compound made up of ONLY hydrogen and carbon atoms

Question 2

4.2 Molecular formula of ethane

Answer 2

C2h6

Question 3

4.2 Empirical formula of ethane

Answer 3

CH3

Question 4

4.2 Displayed formula of ethane

Answer 4

H   H
        /     /
H - C - C - H
        /     /
       H    H

Question 5

4.2 Structural formula of ethane

Answer 5

CH3CH3

Question 6

4.2 General formula of alkanes

Answer 6

CnH2n+2

Question 7

4.3 Homologous series properties

Answer 7

• same general formula
• same functional group (e.g. alkanes)
• trend in boiling point
• same chemical properties (reactivity)
• differ by CH2

Question 8

4.3 functional group

Answer 8

• group of atoms that determines the reactivity of a molecule

Question 9

4.3 isomerism

Answer 9

• same molecular formula, different structural/displayed formula

Question 10

4.6 classifying reactions of organic compounds

Answer 10

Substitution - straight swap
Addition - two things add up to make one molecule
Combustion - produces carbon dioxide and water

Question 11

4.19 general formula of alkanes

Answer 11

CnH2n+2

Question 12

4.20 why are alkanes classified as saturated hydrocarbons

Answer 12

There are only carbon single bonds

Question 13

4.24 general formula for alkenes

Answer 13

CnH2n

Question 14

4.25 explain why alkenes are classified as unsaturated

Answer 14

Because it has a carbon double bond

Question 15

4.27 reaction of alkenes with bromine water to produce dibromoalkanes

Answer 15

• addition reaction

- example: ethene + bromine = dibromoethane

Question 16

why are alkenes more useful than alkanes

Answer 16

• they are more reactive due to the carbon double bond

- they are used to make polymers

Question 17

4.28 how can bromine water be used to distinguish between an alkane and an alkene

Answer 17

• alkane = no change to bromine water (orange)

- alkene - bromine water will be decolourised

Question 18

4.7 what is crude oil

Answer 18

• a mixture of hydrocarbons

Question 19

4.8 fractional distillation

Answer 19

• heat crude oil until it evaporates
• fractionating column is very hot at the bottom and cool at the top
• crude oil enters fractionating column and vapour rises
• hydrocarbons with high boiling points will immediately condense into liquid lower down and are tapped off at the bottom of the column
• hydrocarbons with lower boiling points will rise up the column and condense at the top to be tapped off

Question 20

4.9 names and uses of main fractions

Answer 20

COOLEST TO HOTTEST:

• refinery gases - domestic heating and cooking
• gasoline (petrol) - fuel for cars
• kerosene - fuel in aircraft
• diesel - fuel in larger vehicles
• fuel oil - fuel for large ships and power stations
• bitumen - surface roads and roofs

Question 21

4.10 trend in colour, boiling point and viscosity

Answer 21

longer chain hydrocarbons:

• more viscous
• higher boiling point
• darker in colour
• less volatile

shorter chain hydrocarbons:

• less viscous
• lower boiling point
• light in colour
• more volatile

Question 22

4.11 what is released when fuel is burned

Answer 22

• heat energy

Question 23

4.12 products of complete and incomplete combustion

Answer 23

complete combustion:

• carbon dioxide
• water

incomplete combustion:

• water
• soot
• carbon monoxide

Question 24

4.13 why is carbon monoxide bad

Answer 24

• binds with red blood cells and prevents them from carrying oxygen around the body

Question 25

4.14 what does the temperature in car engines allow

Answer 25

- allows nitrogen and oxygen to react, forming oxides of nitrogen

Question 26

4.15/4.16 sulphur dioxide

Answer 26

- combusting impurities in hydrocarbon fuels results in formation of sulphur dioxide - sulphur dioxide mixes with water vapour in clouds and creates acid rain which poisons plants and animals as well as corroding buildings

Question 27

4.17/4.18 cracking

Answer 27

- more demand for short chain hydrocarbons - long chain hydrocarbons are cracked using high temperatures (600-700) and silica (catalyst) - produces alkenes