C7 redox

Cards (13)

a redox reaction involves reduction and oxidation
oxidation means loss of electrons
reduction means gain of electrons
oxidising agents oxidise other species, so they themselves are reduced, they are electron acceptors
reducing agents reduce other species, so they themselves are oxidised, they are electron donors
oxidation states are numbers which represent the extent to which an element has been oxidised or reduced as part of a compound
the overall oxidation state of a compound is the sum of the individual oxidation states, it should add up to 0 as all compounds are neutral
a negative oxidation state shows the element has gained electrons so has been reduced
a positive oxidation state shows the element has lost electrons so has been oxidised
general rules for oxidation states:
uncombined elements = 0
hydrogen = +1
group 1 = +1
group 2 = +2
aluminium = +3
oxygen = -2
group 7 = -1
half equations are used to show the separate oxidation and reduction reactions that happen as part of a redox reaction, they need to be balanced in terms of elements and charges
the process to write balanced half equations:
balance everything except oxygen and hydrogen
balance oxygen by adding H2O
balance hydrogen by adding H+ ions
balance charges by adding e-
half equations can be combined to determine the overall redox reaction
to combine half equations, multiply one or both half equations by a factor so they have the same number of electrons, then combine and cancel the electrons