C7

Question 1

General formula for carbon atoms and hydrogen atoms

Answer 1

CnH (2n+2)
E.g.
Méthane = CH4
Éthane = C2H6
Propane = C3H8
Butane = C4H10

Question 2

Hydrocarbons

Answer 2

Make up majority of the compounds of crude oils.

Most of these are called alkanes.

Question 3

Crude oil

Answer 3

A finite resource.

Consisting mainly of plankton that was buried in the mud, crude oil is the remains of ancient biomass.

Question 4

Alkanes to alkenes

Answer 4

Long chain alkanes are cracked into short chain alkenes.

Question 5

Alkenes

Answer 5

Hydrocarbons with a double bond (some are formed during the cracking process)

Question 6

Properties of alkenes

Answer 6

More reactive than alkanes and react with bromine water.
Bromine water changes from orange to colourless in the presence of alkenes.
Unsaturated - some carbon - carbon bonds are double bonds.

Question 7

Cracking

Answer 7

Breaking down of long chain hydrocarbons into smaller chains.
Smaller chains more useful.
Done in various methods.

Question 8

Catalytic cracking

Answer 8

Heavy fraction is heated until vaporised.

After vaporisation, vapour is passed over a hot catalyst forming smaller, more useful hydrocarbons.

Question 9

Steam cracking

Answer 9

Heavy fraction heated until vaporised

After vaporisation, the vapour is mixed with steam, heated to high temp forming smaller more useful hydrocarbons.

Question 10

Fractions

Answer 10

Hydrocarbons in crude oil can be split into fractions.
Each fraction has molecules with a similar no. of carbon atoms in them.
The process to do this is called fractional distillation.

Question 11

Alkanes

Answer 11

Saturated - all carbon - carbon bonds are single

A homologous series (same properties and general formula)

Question 12

Separating crude oil

Answer 12

Fractional distillation: the oil is heated to 400 degrees, it becomes a vapour. There is a temp. gradient of cold at the top and hot at the bottom of the fractionating column.
The gases then rise, when they reach their boiling point they condensé and become a liquid.

Question 13

Using fractions

Answer 13

Processed to produce field and feed stick for petrochemical industry:
Gas - LPG, bottled gas.
Gasoline - petrol
Kerosene - aviation fuel
Diesel oil - diesel cars and lorries
Fuel oil - ships
Naptha-solvents, polymers, detergents, prep of rubber compounds

Question 14

Combustion

Answer 14

To burn in oxygen/air to produce carbon dioxide and water.

Question 15

Complete combustion

Answer 15

Burnt with enough/excess oxygen.
Methane + oxygen - water and carbon dioxide
CH4 + 2O2 - 2H2O + CO2

Question 16

Incomplete combustion

Answer 16

Burnt with not enough oxygen.
Methane + oxygen - water + carbon monoxide
CH4 + 1&halfO2 - 2H2O + CO

Methane and oxygen - water + carbon
CH4 + O2 - 2H2O + C

Question 17

Tests: hydrogen, carbon dioxide, water

Answer 17

Hydrogen: lit spill squeaky pop.
Carbon dioxide: bubbles through lime water, lime water turns cloudy.
Water:CuSO4 + 5H2O - CuSO4 . 5H2O

Question 18

Tests: chlorine and oxygen

Answer 18

Chlorine: bleached damp litmus paper
Oxygen: RELIGHTS a LIT spill

Question 19

Decane -

Answer 19

Decane - pentane and propene + ethane

C10H22 - C5H12 + C3H6 + C2 + H4