Topic 3 - Redox Reactions

Question 1

Oxidation Number

Calculate the oxidation number of elements in compounds and ions
The use of oxidation numbers in peroxides and metal hydrides is expected

Answer 1

• Uncombined elements = 0
• Ions = always same as the charge on the ion
• Group 1 = +1
• Group 2 = +2
• Group 3 = +3
• Aluminium = +3
• Fluroine = -1
• Hydrogen = +1 excpet when -1 in hydrides
• Chlorine = -1 except in compounds with F and 0 where it would be positiive
• Oxygen = -2 except when -1 in peroxides and +2 in 0F2

Question 2

Redox reactions involve both reducation and oxidation

Answer 2

Oxidation is loss of electrons
Reduction is gain of electrons

Question 3

Oxidising agents

Answer 3

gain electrons and are reduced themselves

Question 4

Reducing agents

Answer 4

Lose electrons and are oxidised themselves

Question 5

Disproportionation reaction

Answer 5

Involves an element in a single
species being simultaneously oxidised and reduced

Question 6

Half Equations

Answer 6

show reduction and oxidation stages in 2 equations

All have electrons present

Question 7

Half Equation rules

Answer 7

1. Write doen the species before and after the reaction
2. balance any atoms apart from oxygen and hydrogen
3. balance any oxygens with H20
4. balance any hydrogens with H+
5. balance charges with electrons