2.4- Redox

Question 0

What is reduction?

Answer 0

Process of electron gain

It involves a decrease in oxidation number

Question 1

What is oxidation?

Answer 1

Process of electron loss

Involves an increase in oxidation number

Question 2

Rules for assigning oxidation numbers?

Answer 2

1. All uncombined elements have an oxidation number of zero
2. Oxidation number of elements in a compound add up to zero
3. The oxidation number of a monoatomic ion is equal to the ionic charge
4. In a polyatomic ion (CO3 2-) the sum of the individual oxidation numbers of the elements adds up to the charge on the ion

Question 3

What are the elements that have invariable oxidation numbers in their common compounds? And what are their oxidation numbers?

Answer 3

Group 1 metals= +1
Group 2 metals= +2
Al= +3
H=+1 (except metal hydrides are -1)
F= -1
Cl,Br,I= -1 (except when in compounds with O and F)
O= -2 (except in peroxides is -1)

Question 4

Br2 (aq) + 2I- (aq) –> I2 (aq) + 2Br- (aq)

What are the reduction and oxidation half equations?

Answer 4

Reduction:
Br2 (aq) + 2e- –> 2Br- (aq)

Oxidation:
2I- (aq) –> I2 (aq) + 2e-

Question 5

What is an oxidising agent?

Answer 5

An oxidising agent (oxidant) is the species that causes another element to oxidise. It is itself being reduced in the reaction

Oxidising agents are electron acceptors

Question 6

What is a reducing agent?

Answer 6

A reducing agent (reductant) is the species that causes another element to reduce. It itself is oxidised in the reaction

Reducing agents are electron donors

Question 7

How would you solve complex half equations?

Answer 7

Half equations are balanced by adding H+, OH- ions and H2O

In acidic conditions use H+ and H2O