chemistry paper 2 revision

chemistry paper 2 revision

reaction rates

the rate of a reaction is how fast the reactants are changed into products.

reaction rate graphs

the steeper the line the faster the reaction, becomes less steep as reactants are used up, the quickest reactions have the steepest lines and become flat in the least time.

equations for reaction rates

the mean rate of reactions = quantity of reactants used / time taken

the mean rate of

reactions = quantity of product formed / time taken

the mean rate of reaction = change in y / change in x

hydrocarbons

a hydrocarbon is any compound formed from only hydrogen and carbon atoms.

CnH2n+n

the first four alkanes are methane, ethane, propane and butane.

hydrocarbon property change as the chain gets longer 

the shorter the chain is the less viscous it is. the shorter the carbon chain the lower temperature needed to vaporise or condense. the shorter the chain the more flammable the hydrocarbon is.

combustion

complete combustion of any hydrocarbon releases lots of energy the only waste products are carbon dioxide and water vapour.

hydrocarbon + oxygen -> carbon dioxide + water

during combustion hydrogen and carbon are oxidised meaning they gain oxygen.

crude oil

crude oil is a finite resource found in rocks. crude oil is the remains of plants and animals that died millions of years ago. most of the compounds of crude oil are hydrocarbons.

fractional distillation

• the hydrocarbons are separated into fractions each of which contains molecules with a similar number of carbon atoms.
• the oil is heated until most of it has turned into gas. the gases enter a fractionating collum.
  
• in the collum hot at the bottom and cooler upwards.
• the longer hydrocarbons have high boiling points they condense back to liquids and drain out of the collum early on when…