Chemistry: Out There
- Created by: William Page-Brown
- Created on: 11-04-13 16:52
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- Chemistry: out there
- redox reactions
- if electrons are transferred it is a redox reaction
- displacement is a redox reaction the reactive displaces the less
- metal ion reduces
- metal atom oxidised
- rusting of iron
- iron + oxygen +water = hydrated iron oxide
- iron is oxidized oxygen is reduced
- prevention against rusting
- combine with non rusting metals
- paints the metal
- oiling on moving parts
- tin plating
- sacrificial methods used where other metals lose electrons instead
- electrolysis
- copper sulfate can be electrolysed to form copper and oxygen
- cathode negative
- anode positive
- an ionic solid cant be electrolysed because the ions cannot move
- more electrons forms more substance
- more charge = more product
- Q=it
- Q - charge
- i - current
- t - time in seconds
- fuel cells
- hydrogen and oxygen give out energy when they react
- the reaction between H and O2 is exothermic
- main one - hydrogen-oxygen fuel cell
- hydrogen into anode
- oxygen into cathode
- cathode makes OH- ions
- anode makes water and electrons through oxidation
- reduction at cathode oxidation at anode
- REDOX reaction
- reaction produces energy and water
- advantages:efficient, direct energy transfer, little energy loss, no pollution
- disadvantages: may need energy from fossil fuels, may contain poisonous catalysts
- CFC's and ozone layer
- chlorofluorocarbons - CCl2F2
- non toxic, non flammable and unreactive
- used in fridges and air conditioning
- the chlorine could break down the ozone
- reducing the amount of ozone means more UV rays
- more UV can cause skin cancer
- many countries banned CFC's completely
- if a covalent bond is broken evenly, each atom gets a shared electron called a free radical
- free radicals are very reactive
- it is the chlorine free radicals which damage the ozone
- CFC's stay in the atmosphere for a very long time
- use alkanes and HFC's instead
- hardness of water
- forms limescale
- formed by calcium and magnesium ions
- carbon dioxide + water +calcium carbonate -> calcium hydrogencarbonate
- temporary hardness - hydrogencarbonate ion
- permanent hardness - dissolved calcium sulphate
- removed by boiling
- adding sodium carbonate
- both removed by ion exchange resin
- test for hard water
- add 100cm3 water to conical flask
- add 1cm3 soap to water
- repeat until good lather
- record soap needed
- alcohols
- general formula - CnH2n+1OH
- methanol, ethanol, propanol, butanol, pentanol
- fermentation produces ethanol
- oxygen converts ethanol into ethanoic acid
- fractional distillation produces pure ethanol
- ethene reacts with steam to make ethanol
- advantages of fermentation: renewable fuel
- disadvantages of fermentation: slow, not pure, low atom economy
- advantages of hydration: quick, very pure, high atom economy, 95% yeild
- disadvantages of hydration: expensive, non renewable
- fats and oils
- are esters: reacted acid and alcohol
- made from glycerol and fatty acids
- oils do not mix in water
- milk is an oil in water emulsion
- butter is a water in oil emulsion
- vegetable oils can make biodeisel
- fats and oils make soap
- using plant oils
- unsaturated oils contain double bonds
- bromine turns colourless in an unsaturated oil
- vegetable oils are hardened by hydrogenation
- partially hydrogenated oil forms a spreadable margarine
- saturated fats and oils increase cholesterol levels
- detergents
- hydrophilic - loves water
- hydrophobic - hates water
- detergents form strong bonds with water and oils to lift the stain
- dry cleaning covers grease in solvent, then both are removed
- biological detergents work best at low temperatures due to enzymes
- redox reactions
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