Chapter 7: Redox

Question 1

Common oxidation states

Answer 1

H +1 (except -1 in metal hydrides)

Group 1 always +1

Group 2 always +2

Aluminium always +3

Oxygen -2 (except in peroxides, where it is -1 and with fluorine)

Fluorine always -1

Cl, Br, I -1 unless combined with more reacive halogen or with oxygen

Question 2

Uncombined elements

Answer 2

oxidation state is zero

Question 3

Disproportionation

Answer 3

When an element is both oxidised and reduced in the same process.

Cu₂O –> Cu + CuO

Cu₂O: Cu = +1

Cu: Cu = 0 (reduced)

CuO: Cu = +2 (oxidised)

Question 4

O

I

L

R

I

G

Answer 4

Oxidation

Is

Loss (of electrons)

Reduction

Is

Gain (of electrons)

Question 5

Oxidising agents…

Answer 5

… get reduced

… accept electrons

Question 6

Reducing agents…

Answer 6

…get oxidised

…donate electrons

Question 7

spectator ions

Answer 7

do not change state during a reaction. They are ignored in ionic equations; state symbols needed:

AgNO3(aq) + KBr(aq) –> KNO3(aq) + AgBr(s)

when ionic substances dissolve, the ions dissociate:

Ag⁺_(aq) + NO_3^-(aq) + K⁺_(aq) + Br^-_(aq) –> K⁺_(aq) + NO₃^-_(aq) + AgBr_(s)

and then removing spectators to give the ionic equation:

Ag⁺_(aq) + Br^-_(aq) –> AgBr_(s)