Organic Chemistry: Alkanes

Question 1

What kind of hydrocarbons are alkanes?

Answer 1

Saturated (contain no C=C)

Question 2

What are alkanes?

Answer 2

a homologous series of saturated hydrocarbons with the general formula CnH2n+2
They’re very unreactive but do burn and react with halogens

Question 3

What is fractional distillation?

Answer 3

Process of separating crude oil into groups of hydrocarbons with a similar number of carbon atoms

Question 4

What is petroleum?

Answer 4

(It’s crude oil)

A mixture consisting mainly of alkane hydrocarbons that can be separated by fractional distillation.

Question 5

Processes involved in fractional distillation

Answer 5

Evaporation
Condensation
Collection

Question 6

What happens in evaporation, condensation and collection of fractional distillation?

Answer 6

Evaporation

Crude oil heated until it evaporated

Question 7

Fractions in fractional distillation

Answer 7

Gases 
Petrol (gasoline) 
Naphtha 
Kerosene (paraffin)
Gas oil (diesel) 
Mineral oil (lubricating)
Residue (fuel oil, wax & grease, bitumen)

Question 8

What are long-chain hydrocarbons?

Answer 8

Hydrocarbons with lots of carbon atoms

Question 9

What are short-chain hydrocarbons?

Answer 9

Hydrocarbons with few carbon atoms

Question 10

Uses of fractions in fractional distillation

Answer 10

Gases - camping gas
Petrol (gasoline) - petrol
Naphtha - processed to make petrochemicals
Kerosene - jet fuel, petrochemicals, central heating fuel
Gas oil- diesel fuel, central heating fuel

Question 11

Combustion is a scientific term for?

Answer 11

Burning

Question 12

What happens when you burn a hydrocarbon?

Answer 12

Complete or incomplete combustion

Question 13

Products of complete combustion

Answer 13

Produces a blue flame

Produces carbon dioxide and water

Question 14

Products of incomplete combustion

Answer 14

Gives an orangey-smoky flame ( due to small particles of carbon glowing red hot)

Question 15

Why is incomplete combustion combustion more likely with longer chain alkanes?

Answer 15

They need more oxygen to combust completely

Question 16

What is internal combustion engine?

Answer 16

Combustion of alkanes power cars via internal combustion engines

Question 17

Products of internal combustion engine

Answer 17

NOx (Nitrous oxide), CO, carbon & unburned hydrocarbons

Question 18

Nitrous oxides from internal combustion engine react with what?

Answer 18

Ozone at ground level. Ozone irritates eyes and can cause lung damage

Question 19

What are flue gases?

Answer 19

Gases that come out of chimneys, also produced as industrial waste. They often contain sulfur dioxide. Sulfur dioxide dissolved in water to make sulfuric acid. This then falls as acid rain, destroys trees and vegetation.

Question 20

How are chemicals removed from internal combustion engines?

Answer 20

Catalytic converters used to remove gaseous pollutants from internal combustion engines.

Remove sulfur dioxide by reacting with calcium oxide or calcium carbonate. SO2 is acidic and CaO is basic.
CaO + SO2 —> CaSO3

Question 21

How can sulphur dioxide be removed from flue gases

Answer 21

Remove sulfur dioxide by reacting with calcium oxide or calcium carbonate. SO2 is acidic and CaO is basic.
CaO + SO2 —> CaSO3

Question 22

What is cracking?

Answer 22

Cracking involves break C-C bonds in alkanes

Question 23

Thermal cracking?

Answer 23

Thermal cracking takes place at high pressure and high temperature and produces a high percentage of alkenes (and few alkanes)

Question 24

Catalytic cracking

Answer 24

Catalytic cracking takes place at a slight pressure, high temperature & in presence of zeolite catalyst