Alkenes

Question 1

Describe combustion of alkenes

Answer 1

• produces unburnt carbon particles
  = because of incomplete combustion
• means alkenes burn in air with a smoky flame

Question 2

Describe alkenes with water (hydration)

Answer 2

• water must be in form of steam
• temp must be 300 Celsius
• pressure 70 atmospheres
• use phosphoric acid as a catalyst
• reaction is reversible

To increase yield of ethanol any untested ethene and steam are passed back through catalyst

Question 3

Uses of alcohols

Answer 3

• fuels
• solvents

Question 4

Describe fermentation of sugar

Answer 4

• start with sugar solution and mix with yeast
• yeast converts sugar solution to an ethanol solution
• co2 also produced
• temp should be 30
• reaction must take place in anaerobic conditions

Question 5

Adv and dis of fermentation

Answer 5

• low temp means doesn’t require a lot of energy
• sugar for reaction comes from plants
  = renewable
• product is an aqueous solution to ethanol
  = must purify ethanol by distillation
  = requires a lot of energy

Question 6

Adv of making ethanol through hydration

Answer 6

• reaction produces a high yield of ethanol
  BUT
• requires a high temp
  = a lot of energy

Question 7

What happens when alcohols react with oxidising agents

Answer 7

• produce carboxylic acid and water

Question 8

Describe combustion of alcohols

Answer 8

• release energy when combusted
• combusting in air produces co2 and water

Question 9

Alkene main use

Answer 9

Used to makes polymers

Question 10

How to test for alkenes

Answer 10

• use bromine water which is orange
• if we shake alkene with bromine water
  = bromine water turns colourless

Question 11

Product of ethene and water

Answer 11

Ethanol
= used in alcoholic drinks

Question 12

Describe hydrogenation

Answer 12

Needs to be 150C
Nickel catalyst
React alkene with hydrogen
= produce alkane

Question 13

Describe alcohols in water

Answer 13

Soluble in water and form neutral solutions
As the number of carbon atoms increases the solubility decreases

Question 14

Properties of alcohols

Answer 14

Flammable
Soluble
Oxidised to form carboxylic acids

Question 15

Describe flammability of alcohols

Answer 15

Undergo complete combustion to form co2 and h2o