Topic 3: Redox I

Question 1

What is meant by the term ‘oxidation number?’

Answer 1

Oxidation state shows the total number of electrons which have been removed from an element (a positive oxidation state) or added to an element (a negative oxidation state) to get to its present state.

Question 2

What happens to electrons in oxidation

Answer 2

Electrons are lost

Question 3

What happens to electrons in reduction

Answer 3

Electrons are gained

Question 4

What are oxidising agents?

Answer 4

They facilitate the oxidation of another species in the reaction
They are reduced - gain electrons

Question 5

What are reducing agents?

Answer 5

They facilitate the reduction of another species in the reaction
They are oxidised - lose electrons

Question 5

What are the oxidation numbers of H and O in H2O2

Answer 5

H = +1
O = -1

Question 6

What is a disproportionation reaction?

Answer 6

When the same element is both oxidised and reduced

Question 7

What charge does a metal ion form?

Answer 7

They form positive ions by loss of electrons with an increase in oxidation number

Question 8

What charge does a non-metal ion form?

Answer 8

They form negative ions by gain of electrons with a decrease in oxidation number

Question 9

Writing ionic equations in acidic conditions

Answer 9

1. calculate oxidation states on either side of equation
2. Balance the element being oxidised
3. Balance electrons
4. Balance oxygen, by adding H2O molecules
5. Balance hydrogen, by adding H+ ions
6. Check the charges are the same either side of the equation