Alkanes and isomerism

Question 1

What is meant by the term Hydrocarbon?

Answer 1

Compounds containing hydrogen and carbon only.

Question 2

Give the name of the substance from which alkanes are obtained.

Answer 2

Crude oil

Question 3

Give the name of the process from which paraffin, petrol, bitumen, naphtha is obtained

Answer 3

Fractional distillation

Question 4

Sate the meaning of the term structural isomers.

Answer 4

Compounds with the same molecular formula but different structural formula.

Question 5

State two characteristics of a homologous series.

Answer 5

Same General formula, Chemically similar / same (chemical) reactions, Same functional group, Trends in physical properties.

Question 6

Name and outline the technique used to separate isooctane from a mixture of octane and isooctane.

Answer 6

Fractional or simple distillation, the one with lower boiling points boils first (or reaches the top of the column first) this then condenses and collects.

Question 7

Outline how different fractions are obtained by fractional distillation.

Answer 7

Crude oil is heated to vaporise it, the vapour passes into fractionating column, top of tower is cooler than bottom or negative temperature gradient, fractions separated by boiling points.

Question 8

Sate the meaning of the term functional group isomers.

Answer 8

Same molecular formula, but different functional group.

Question 9

Explain why the melting point of straight chain alkanes increase with size.

Answer 9

More Van Der Waals’ forces between molecules.

Question 10

What is meant by the term Chain isomers?

Answer 10

Compounds with the same molecular formula but different arrangement of the carbon skeleton.

Question 11

What is meant by the term position isomers?

Answer 11

Compounds with the same molecular formula but different structures due to different positions of the same functional group on the same carbon skeleton.

Question 12

What are the products of complete combustion?

Answer 12

Water and Carbon dioxide

Question 13

What are the products of incomplete combustion?

Answer 13

Water, Carbon (soot), Carbon monoxide

Question 14

What are the environmental problems of Carbon dioxide and water?

Answer 14

These are greenhouse gases and they contribute to Global warming.

Question 15

What is a problem of carbon (soot)?

Answer 15

Exacerbates asthma/ breathing problems/ damages lungs/ smog/ smoke/ global dimming.

Question 16

Explain how oxides of nitrogen are formed.

Answer 16

Nitrogen and oxygen (from air) react at high temperatures.

Question 17

Explain why the sulphur compounds found in crude oil should be removed from the fractions before they are used for central heating fuel.

Answer 17

SO2 is produced from the combustion and this causes acid rain.

Question 18

What is a structural formula?

Answer 18

A formula that shows the arrangement of atoms in the molecule of a compound. CH3CH2CH3.

Question 19

How is sulphur dioxide removed from power stations?

Answer 19

Neutralise with calcium oxide (flue gas desulphurisation).

Question 20

Write an equation to show how carbon monoxide and nitrogen oxides react together in a catalytic converter.

Answer 20

2CO + 2NO → 2CO2 + N2

Question 21

Identify a catalyst used in a catalytic converter.

Answer 21

Platinum, Palladium or Rhodium.

Question 22

Why do blockages in air intakes affect the performance of engines?

Answer 22

Less energy given out by the fuel to burn more fuel to get the same energy / increased costs due to need to use more fuel.

Question 23

Explain the main economic reason why alkanes are cracked.

Answer 23

To produce substances which are (more) in demand.

Question 24

State why a high temperature is needed for cracking reactions to occur.

Answer 24

To break bonds.

Question 25

State the conditions and the products for thermal cracking.

Answer 25

High temperature and high pressure, products are mainly alkenes.

Question 26

A very thin layer of the metals is used on a honeycomb ceramic support in a catalytic convertor. Explain why.

Answer 26

To reduce amount of metals needed and to give catalyst a larger surface area : volume ratio.

Question 27

What are alkenes used for?

Answer 27

Making polymers.