Redox 1

Question 1

What is oxidation number?

Answer 1

Oxidisation number gives the oxidation state of an element or ionic substance

Question 2

Calculating oxidisation number rules

Answer 2

1. Oxidation number of an element is 0
2. Oxidation numbers in a neutral compound add to 0
3. Oxidation numbers in a charged compound add to the charge
4. Hydrogen: +1
5. Oxygen: -2
6. Halogens: -1
7. Group 1 metals: +1
8. Group 2 metals: +2
9. Aluminium: +3

Question 3

Calculating oxidisation number rules (exceptions)

Answer 3

1. Oxygen has an oxidation number of -1 in peroxides (ex. H₂O₂)
2. Hydrogen has an oxidation number of -1 in metal hydrides

Question 4

s-block and p-block oxidation/reduction

Answer 4

• s-block elements generally lose electrons and are oxidised, forming species with positive oxidation numbers
• p-block non-metals generally gain electrons, so are reduced and form species with negative oxidation numbers

Question 5

What is oxidisation?

Answer 5

The loss of electrons

Question 6

What is reduction?

Answer 6

The gain of electrons

Question 7

What are oxidising agents?

Answer 7

An oxidising agent:
* accepts electrons from the species being oxidised
* gains electrons and is therfore reduced

Question 8

What are reducing agents?

Answer 8

An reducing agent:
* donates electrons to the species being reduced
* loses electrons and is therfore oxidised

Question 9

What is a disproportionation reaction?

Answer 9

A disproportionation reaction involves an element in a single species being simultaneously oxidised and reduced

Question 10

Why are oxidation numbers a useful concept?

Answer 10

oxidation numbers help to classify reactions as redox and as disproportionation