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Chemical changes (Oxidation and Reduction in terms of electrons (Oxidation…
Chemical changes
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Electrolysis
The process
when an ionic compound is melted or dissolved in water the ions are free to move about within the liquid or solution. these liquids are able to conduct electricity and are called electrolytes
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when a simple ionic compound is electrolysed in molten state using inert electrodes, the metal is produced at the cathode and the non-metal at the anode
extraction of metals
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electrolysis is used if the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon
large amounts of energy are used in the extractions process to melt the compounds and to produce the electrical current
aluminium is manufactured by the electrolysis of molten mixtures of aluminium oxide and cryolite using carbon as the positive electrode
the anode is made of carbon and needs replacing regularly as it reacts with oxygen to produce carbon dioxide
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Reaction of acids
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Soluble Salts
- can be made from acids by reacting them with solid insoluble substance such as: metals, metal oxides, hydroxides or carbonates
- the solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt
- salt solutions can be crystallised to produce solid salts
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Strong and weak acids
Strong acid: completely ionised in queues solution - hydrochloric HCL, nitric HNO3, sulfuric H2SO4
Weak acid: is only partially ionised in aqueous solution - ethnic, citric and carbonic acids
for a given concentration of aqueous solutions, the stronger an acid, the lower the pH
As the pH decreases by one unit, the hydrogen ion concentration of the solution increases by a factor of 10
- Factor H+ ion concentration changes by 10 ^-x
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