Chemistry Paper 2

• rate of reaction is change in quantity divided by time
• hydrochloric acid + sodium thiosulfate = cloudy white
• increasing rate of reaction:

  • increase surface area
  • increase temperature
  • use a catalyst
• gradient is the rate of reaction
• Le Chatelier's principle: If a system is in equilibrium, any change in the conditions will result in a change in the position of equilibrium
• When equilibrium is reached, the overall quantity of both sides will not change, unless:

  • you increase pressure
  • change concentration
  • change temperatute
• increasing temperature favours endothermic as heat is needed
• one direction is always endothermic and the other is exothermic
• crude oil is made from plankton buried underwater and compressed for a while
• hydrocarbons consist of only hydrogen and carbon
• the two types of hydrocarbon are alkane and alkene
• alkenes have double bonds
• alkanes are made up of single covalently bonded carbon atoms surrounded by hydrogen
• alkanes are saturated
• alkenes are unsaturated
• methane - 1 carbon
• ethane - 2 carbon
• propane - 3 carbon
• butane - 4 carbon
• general formula for alkanes: Cn H2n + 2
• the hydrocarbons in crude oil must be separated before use
• the fractionating column gets colder as you get higher
• longer alkanes have higher boiling points due to more energy to break stronger intermolecular forces, so they recondense lower down the column
• LPG

  Petrol

  Kerosine

  Diesel

  Heavy fuel

  Bitumen
• complete combustion =

  fuel + oxygen > carbon dioxide + water
• incomplete combustion

  fuel + oxygen > carbon monoxide + water
• longer alkanes have higher viscosity
• shorter alkanes are more flammable
• hydrocarbons can also be use to make solvents lubricants detergents and polymers
• an alkene is a hydrocarbon with at least one double covalent bond
• alkenes end with - ene
• general formula for alkenes Cn H2n
• alkene turn bromine water from orange to colourless
• chlorine and iodine react similarly while water reacts with an alkene to form an alcohol
• there is a greater demand for shorter alkanes compared to longer ones
• cracking is used to breakdown longer alkanes into shorter alkanes
• we use an alkene to break down alkanes
• catalytic cracking uses a zeolite catalyst at 550
• steam cracking uses no catalyst and at higher temperatures