P.P Notes Redox Reactions

Question 1

What is a redox reaction?

Answer 1

A reaction involving both oxidation (loss of electrons) and reduction (gain of electrons)

Question 2

What does OIL RIG stand for in redox chemistry?

Answer 2

Oxidation Is Loss
Reduction Is Gain
(of electrons)

Question 3

In the reaction between Mg and HCl, which species is oxidised and which is reduced?

Answer 3

Mg is oxidised (loses electrons)
HCl is reduced (gain electrons)

Question 4

What is a half-equation?

Answer 4

An equation showing the loss or gain of electrons by a species during a redox reaction

Question 5

Write the half-equations for Mg reacting with HCl

Answer 5

Oxidation: Mg -> Mg2+ + 2e-
Reduction: 2H+ 2e- -> H2

Question 6

What is a reductant (reducing agent)?

Answer 6

A substance that donates electrons and causes another species to be reduced

Question 7

What is an oxidant (oxidising agent)?

Answer 7

A substance that gains electrons and causes another species to be oxidised

Question 8

What is an oxidation number?

Answer 8

A number that represents how many electrons an atom has gained or lost

Question 9

What are the main rules for assigning oxidation numbers

Answer 9

Free elements = 0
Ions = same as charge
H = +1 (except in metal hydrides: -1)
O = -2 (except peroxides: -1 and in F2O: +2

Question 10

What is corrosion?

Answer 10

The oxidation of metals in the presence of air and moisture to form metal oxides.