DF - Alkanes

Question 1

Explain why the straight chain isomer has a higher boiling point than any of its branched chain structural isomers

Answer 1

Branched chains have less surfaced area
Branched chains have less Van Der Waal’s forces

Question 2

Explain why the straight chain isomer is converted by the petroleum industry into its branched chain isomers

Answer 2

Branched chain isomers have more efficient combustion

Question 3

Suggest, with the aid of an equation, how NO is formed within an aeroplane engine

Answer 3

N2 + O2 -> 2NO

Question 4

Name one other bromine-containing organic product which is formed when methane reacts with bromine

Answer 4

Dibromomethane

Question 5

Answer 5

Question 6

State and explain the trend in boiling points of alkenes

Answer 6

Boiling point increases with chain length
Due to more intermolecular forces

Question 7

Formation of cyclic alkanes equation

Answer 7

Alkane -> cyclic alkane + H2

Question 8

What is meant by the term fractional distillation

Answer 8

Separation by difference in boiling point

Question 9

Explain why 2-methylhexane and 2,3-dimethylpentane have different boiling points

Answer 9

If branched, less points of contact
Less intermolecular bonds

Question 10

Describe, with the aid of a diagram, the formation of a pi bond

Answer 10

Question 11

Describe, with the aid of a suitable example, why some alkenes show cis-trans isomerism

Answer 11

• cis & trans diagram
  a double bond restricts rotation
  Each C in the C=C double bond is bonded to two different atoms or groups

Question 12

State the type of reaction

Answer 12

Free radical substitution

Question 13

Outline the process of processing the fractions from crude oil

Answer 13

• High temps or a catalyst is required
• Cracking occurs
• Formation of cyclic structure

Question 14

State clearly the industrial importance of the products formed in isomerisation

Answer 14

• USed in fuels
• More efficient fuels
• H2 used in Haber process

Question 15

Draw compound A

Answer 15

Question 16

State a suitable reagent for dehydrating alcohol

Answer 16

H2SO4

Question 17

Write a balanced equation for the dehydration of cyclohexanol

Answer 17

Question 18

Explain why the isomer with the most branches has the lowest boiling point

Answer 18

The more branches, the less energy required to break the bonds
As branched alkanes have less Van Der Waal’s forces

Question 19

Suggest one reason why oil companies reform alkanes

Answer 19

Better fuels

Question 20

How to calculate the percentage by mass of oxygen in a compound

Answer 20

(Mr of oxygen / total Mr) x100

Question 21

State what happens to the free radicals in the termination steps

Answer 21

React with each other

Question 22

EXplain why, in the long term, ethanol could replace oil-based fuels

Answer 22

Oil is non-renewable
Ethanol is renewable from plants

Question 23

Equation for ethene being converted into ethanol

Answer 23

C2H4 + H2O -> C2H5OH

Question 24

What conditions are needed for ethene to be converted into ethanol?

Answer 24

Phosphoric acid catalyst
Steam

Question 25

Answer 25

1 degree higher
As 1 less branch

Question 26

State why branched chain alkanes and cycloalkanes are more useful than straight chain alkanes

Answer 26

More efficient
More volatile