Chapter 6 - alkanes

Question 0

Outline some uses for alkanes

Answer 0

Fuels, lubricants, starting materials

Question 1

Define the term alkane

Answer 1

a saturated hydrocarbon with C-C and C-H single bonds only taking the formula CnH2n+2

Question 2

What is the main source of alkanes?

Answer 2

Crude oil

Question 3

What physical properties of alkanes allows them to be separated from a mixture of crude oil?

Answer 3

Different boiling points

Question 4

Why do branched hydrocarbons have a lower boiling point?

Answer 4

They’re loosely packed so the van der Waals forces aren’t as effective

Question 5

Define the term fraction

Answer 5

A mixture of hydrocarbons over a particular range of boiling points during fractional distillation

Question 6

Describe the 3 main stages in fractional distillation

Answer 6

Crude oil is heated and vaporised, the gases enter the bottom of the fractionating column as the gases go up the column the temperature decreases, they condense at different fractions according to their boiling points proportional to the length of hydrocarbon

Question 7

Explain why long chain alkanes are cracked

Answer 7

To make shorter chain hydrocarbons which are in greater demand therefore more profitable

Question 8

What are short chain alkanes used for?

Answer 8

camping gas

Question 9

What are medium chain alkanes used for?

Answer 9

Fuels

Question 10

What are long chain alkanes used for?

Answer 10

Paraffin

Question 11

What type of cracking produces a high proportion of alkenes?

Answer 11

Thermal

Question 12

Outline and describe the catalyst used in cracking

Answer 12

Zeolite, honeycomb structure with enormous surface area

Question 13

What is the test for alkenes?

Answer 13

Decolorisation of bromine solution

Question 14

What type of cracking produces a high proportion of branched alkanes and cycloalkanes?

Answer 14

Catalytic

Question 15

Explain the cause and the effect of carbon monoxide

Answer 15

Incomplete combustion, it’s poisonous and it increases asthma/ breathing problems

Question 16

Outline the cause and effect of nitrogen oxides

Answer 16

High temperature engine –> acid rain and smog

Question 17

Outline the cause and effect of sulphur dioxide and suggest how it could be treated

Answer 17

Sulphur impurities in fuels –> acid rain, removed with limestone/ calcium oxide (neutralisation)

Question 18

Explain why CO2 is bad for the atmosphere

Answer 18

It’s a greenhouse gas and therefore contributes to global warming

Question 19

What catalyst is used in a catalytic converter?

Answer 19

Platinum

Question 20

What are catalytic converters used for?

Answer 20

Removal of carbon monoxide, unburnt hydrocarbons and nitrogen oxides

Question 21

Explain the structure of the catalyst in the catalytic converter

Answer 21

The platinum is coated on a ceramic honeycomb to reduce cost and increase surface area