Redox

Question 1

OILRIG

Answer 1

Oxidation is loss (of electrons)

Reduction is gain (of electrons)

Question 2

Reducing agent

Answer 2

Lose electrons and are oxidised themselves

Question 3

Ex

Ca + 1/2O2 > CaO

Ca > Ca2+ + 2e-

1/2O2 + 2e- > O2-

Answer 3

Calcium is being oxidised as it is losing electrons

Oxygen is being reduced as it is gaining electrons

Ca = reducing agent
1/2 O2 = oxidising agent

Question 4

Oxidising agent

Answer 4

Gain electrons and are reduced themselves

Question 5

Uncombined elements

Answer 5

Oxidation number always O

E.x. cl2, O2

Question 6

Ions

Answer 6

Number is same as charge on ion

E.g. Cl- = -1
Ca2+ = +2

Question 7

Group 1

Answer 7

Always +1

E.x. KCl

Question 8

Group 2

Answer 8

Always +2

E.x. CaO

Question 9

Aluminium

Answer 9

Always +3

E.x. Al2O3

Question 10

Hydrogen

Answer 10

+1 (except in hydrides where it is -1)

E.x. HF

Hydride ex: NaH

Question 11

Fluorine

Answer 11

Always -1

E.x. KF

Question 12

Oxygen

Answer 12

• 2 (except in peroxides where -1 and +2 in OF2)
  e. g. Li2O

O has value of -1 in H2O2

Question 13

E.g. SO4 2-

Answer 13

All the oxidation states must add to overall charge of molecule

O= (-2x4) = -8
-8 -> -2 = 6 so, +6

Question 14

Transition metals

Answer 14

Variable oxidation states

Question 15

Charge of metal

Answer 15

Represented with Roman numeral

E.g. Charge of +3 = Iron (III) oxide

Question 16

ClO2- systematic name

Answer 16

As chlorine is bonded to oxygen, add -ate to the end

Chlorate (III)

Question 17

Reduction

Answer 17

Decrease in oxidation number

Question 18

Oxidation

Answer 18

Increase in oxidation number

Question 19

Metals + acids

Answer 19

Oxidised and form salt and hydrogen gas

Question 20

Chlorine

Answer 20

-1 unless with fluorine, becomes +