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Slide 2

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The Rules
Species Oxidation number
Uncombined element 0
Combined oxygen -2
Combined hydrogen +1
Simple ion Ionic charge
Combined fluorine -1…read more

Slide 3

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Remov
e
electro
ns
4
·
· 3Cu² +
Combi
2Fe
ne
Fe³ +
equati
3Cu
ons
· 3Cu² +
3
· 2Fe +
Balanc
6e
e
the
Fe³ +
electro
3Cu +
ns
6e 2
· 2Fe
2Fe³ +
·
Given
6e
· equati
3Cu² +
ons
6e
· Fe
3Cu 1
Fe³ +
3e
· Cu² +
2e
Cu
Using half equations…read more

Slide 4

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Using oxidation numbers
Question from question
· HI + HSO HS + I
Identify oxidation number changes
· 2HI + HSO HS + I
· +6 -2 (-8)
· 2 x -1 0x2 (+2)
Balance oxidation number changes
· 2HI + HSO HS + I
· +6 -2 (-8)
· 8 x -1 0x2x4 (+8)
Check balancing
· 8HI + HSO 4HS + I + 4HO…read more

Slide 5

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Extra information
· 4HO is added as there was an extra 8H and
4O
· If the equation is short of a H then H, OH,
and HO
· Acidic conditions add H
· Alkaline conditions add OH…read more

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