Alkenes Flashcards
Describe combustion of alkenes
- produces unburnt carbon particles
= because of incomplete combustion - means alkenes burn in air with a smoky flame
Describe alkenes with water (hydration)
- 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
Uses of alcohols
- fuels
- solvents
Describe fermentation of sugar
- 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
Adv and dis of fermentation
- 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
Adv of making ethanol through hydration
- reaction produces a high yield of ethanol
BUT - requires a high temp
= a lot of energy
What happens when alcohols react with oxidising agents
- produce carboxylic acid and water
Describe combustion of alcohols
- release energy when combusted
- combusting in air produces co2 and water
Alkene main use
Used to makes polymers
How to test for alkenes
- use bromine water which is orange
- if we shake alkene with bromine water
= bromine water turns colourless
Product of ethene and water
Ethanol
= used in alcoholic drinks
Describe hydrogenation
Needs to be 150C
Nickel catalyst
React alkene with hydrogen
= produce alkane
Describe alcohols in water
Soluble in water and form neutral solutions
As the number of carbon atoms increases the solubility decreases
Properties of alcohols
Flammable
Soluble
Oxidised to form carboxylic acids
Describe flammability of alcohols
Undergo complete combustion to form co2 and h2o
