Last minute chemistry revision!

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  • Created on: 07-01-14 18:46
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Ionic is the electrostatic attraction between oppositely charged ions. Metal + metal/non-metal.
Covalent is the attraction of two positive nuclei for a shared pair of electrons. Non-metal + non-metal.
Metallic is the attraction of two positive metal ions for a 'sea' of delocalised electrons.
Covalent bonds holding the atoms together are very strong but the intermolecular forces are weak, therefore only a low
temperature is needed to separate the molecules when they are melted or boiled.
All ionic compounds are solid at room temperature.
Relative atomic mass= the weighted mean mass of an atom of an element relative to 1/12 the mass of an atom of carbon-12.
Diamond- used in cutting tools and in jewellery
Graphite- used in electrodes and as a lubricant
The iron compound present in rust is iron (III) oxide. It rusts in the presence of oxygen and water, and salts speed up the process.
Methods used to prevent rusting are painting, coating in oil, attaching magnesium blocks, alloying the iron with chromium and
nickel, using a sacrificial metal and galvanising.
When hydrogen chloride is dissolved in water, the ions H+ and Cl- are present. This makes the litmus paper turn red as it is
hydrochloric acid.
When it is dissolved in methylbenzene, the litmus paper will be blue because there is no reaction and no H+ ions are formed so
the solution does not display acidic properties.
Hydration of ethene= phosphoric acid, 300C, 60-70 atmospheres
Dehydration of ethanol= hot aluminium oxide
Haber process= iron catalyst, 450C, 200 atmospheres
Contact process= vanadium (V) oxide catalyst, 450C, 2 atmospheres
Cracking= silica/alumina, 600-700C
Test for chlorine= damp litmus paper turns white/moist starch iodide paper turns blue

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Test for ammonia= damp red litmus paper turns blue/damp universal indicator paper turns purple
Cations flame tests= lithium-red, potassium-lilac, calcium-brick red, sulphur-yellow/orange
Cations precipitation with sodium hydroxide= copper (II)- blue, iron (II)- green, iron (III)- brown
Halide ions by precipitation with dilute nitric acid + silver nitrate= chlorine-white, bromine-cream, iodine- yellow
Sulphate ions by precipitation with hydrochloric acid + barium chloride= white precipitate
Cracking is important because:
It produces shorter molecules which have a higher demand and are used to make petrol for cars…read more


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