Alkanes

Question 1

What is an empirical formula?

Answer 1

The simplest whole number ratio of atoms of each element in a compound

Question 2

What is a molecular formula?

Answer 2

The formula that shows the actual number of atoms of each element in a molecule

Question 3

What is a general formula?

Answer 3

A generalised formula which enables you to work out the molecular formula of a compound within a homologous series

Question 4

What is a structural or shorthand formula?

Answer 4

A formula showing the arrangement of atoms in a substance without showing the bonds. E.g. CH₃CH₂CH₃

Question 5

What is a displayed formula?

Answer 5

A formula showing the arrangement of atoms in a substance and all the bonds E.g.

Question 6

What is a skeletal formula?

Answer 6

A simplified version of a displayed formula where straight lines represent carbon-carbon bonds e.g.

Question 7

What is a hydrocarbon?

Answer 7

A compound made of atoms of hydrogen and carbon only

Question 8

What is an alkane?

Answer 8

A hydrocarbon with only single bonds.

Question 9

What is chemical nomenclature?

Answer 9

The process of naming different organic compounds

Question 10

Name a given branched alkane

Answer 10

Assign parent chain, assign branches a number and add as prefixes

Question 11

What is isomerism?

Answer 11

When molecules have the same atoms but they are arranged differently in space

Question 12

What is structural isomerism?

Answer 12

Where isomers have the same molecular formula but a different structure

Question 13

What are the three types of structural isomerism?

Answer 13

Chain, position and functional

Question 14

What is a saturated hydrocarbon?

Answer 14

A hydrocarbon with only single bonds

Question 15

What is crude oil?

Answer 15

A mixture of mainly alkanes that can be separated by fractional distillation

Question 16

What is fractional distillation?

Answer 16

The process of separating the alkanes in crude oil by use of their different melting points

Question 17

What is cracking?

Answer 17

The process of breaking C-C bonds in alkanes to make shorter molecules

Question 18

What are the two types of cracking?

Answer 18

Thermal cracking and catalytic cracking

Question 19

How is thermal cracking carried out?

Answer 19

At high pressure and temperature

Question 20

What is thermal cracking used for?

Answer 20

Producing a high percentage of alkenes

Question 21

How is catalytic cracking carried out?

Answer 21

Slight pressure, high temperature, zeolite catalyst

Question 22

What is catalytic cracking used for?

Answer 22

Production of motor fuels and aromatic hydrocarbons

Question 23

Why is cracking carried out?

Answer 23

The products of cracking are in greater demand than the long chain alkanes

Question 24

What is combustion?

Answer 24

The exothermic reaction of a fuel with oxygen

Question 25

What is complete combustion?

Answer 25

A combustion reaction where there is enough oxygen to ensure products are purely carbon dioxide and water

Question 26

What is incomplete combustion?

Answer 26

A combustion reaction where the lack of oxygen results in products other than carbon dioxide and water

Question 27

What can the products of incomplete combustion be?

Answer 27

Carbon monoxide, carbon

Question 28

Which pollutants are produced by the internal combustion engine?

Answer 28

Nitrogen oxides, carbon monoxide, carbon, unburned hydrocarbons

Question 29

What is the purpose of a catalytic convertor?

Answer 29

To remove gaseous pollutants produced by internal combustion engines

Question 30

How is sulphur dioxide released from combustion engines?

Answer 30

Through the combustion of hydrocarbons containing sulphur impurities

Question 31

What is a flue gas?

Answer 31

The gas released from large industrial plants and power plants

Question 32

How can sulphur dioxide be removed from flue gases?

Answer 32

By using calcium oxide or calcium carbonate to neutralise it

Question 33

What is a free radical?

Answer 33

A reactive species containing an unpaired electron

Question 34

How are free radicals signaled?

Answer 34

By use of a ∙ e.g.. Cl∙

Question 35

How are chlorine free radicals produced?

Answer 35

Exposure to UV light

Question 36

What is free radical substitution?

Answer 36

Where an atom bonded to a carbon is substituted for a free radical atom

Question 37

Which steps are involved in a free radical substitution?

Answer 37

Initiation, propagation, termination

Question 38

What is an initiation step?

Answer 38

The generation of a free radical

Question 39

Give an example of an initiation step

Answer 39

Cl₂ → 2Cl∙

Question 40

What is a propagation?

Answer 40

Intermediate steps in a free radical reaction which cause the regeneration of the original free radical

Question 41

Give an example of a propagation

Answer 41

CH₄ + Cl∙ → CH₃∙ + HCl, CH₃∙ + Cl₂ → CH₃Cl + Cl∙

Question 42

What is a termination?

Answer 42

A reaction involving two free radicals and resulting in no free radicals

Question 43

Give an example of a termination

Answer 43

CH₃∙ + Cl∙ → CH₃Cl

Question 44

Why do free radical substitutions result in impure products

Answer 44

Because there are many possible side reactions e.g. further substitution with chlorine or alkyl radical-radical reactions