C5 Oxidation, reduction and redox

What is oxidation

Gain of oxygen / loss of electrons

What is reduction

Removal of oxygen / gain of electrons

If Fe2+ → Fe3+ + e- then what happened

fe2+ was oxidised

What is the oxidation state of an elemental atom

0

What is the oxidation state of a monatomic ion equal to

Charge on the ion

Oxidation state of Cl-

-1

Oxidation state of Mg2+

+2

Sum of oxidation states of atoms in a compound

0

Sum of oxidation states of all atoms in a polyatomic ion is equal to

Charge on the ion

Sum of oxidation states on CO3 2-

-2

Oxidation state of group 1 metal atom in compound

+1

Oxidation state of group 2 metal atom in a compound

+2

Oxidation state of sodium in NaOH

+1

Oxidation state of magnesium in MgCl2

+2

Oxidation state of oxygen atom in compound

-2 except for in peroxides or compound with fluorine

When is oxidation state of oxygen atom not -2

Peroxides (-1) or when combined with fluorine (+2)

Oxidation state of oxygen in peroxides

-1

Oxidation state of oxygen in compound with fluorine

+2

Oxidation state of hydrogen atoms in compound

+1 except for metal hydrides

Oxidation state of hydrogen in metal hydride

-1

When is oxidation state of hydrogen in compound not +1

Metal hydride (-1)

Example of metal hydride

MgH2

What has happened to an element if it increases its oxidation state

Oxidised

What has happened to an element if it has decreases its oxidation state

Reduced

What is disproportionation

One species/element is oxidised and reduced at the same time

What is an oxidising agent

Loses oxygen / accepts e-

What is a reducing agent

Accepts oxygen / loses electron

Good oxidising agents should

Tend to accept e- (get reduced)

Good reducing agents should

Tend to lose e- (get oxidised)

What group would make a good oxidising agent

Group 17 - tends to get reduced/gain e-

Which group would make a good reducing agent

Group 2 - tends to lose e- (get oxidised)

If an ion becomes more negatively charged has it been oxidised or reduced

Reduced

If an ion becomes more positively charged has it been oxidised or reduced

Oxidised