Topic 3: Redox I

Question 1

Is loss of electrons oxidation or reduction

Answer 1

Oxidation

Question 2

Define : oxidising agent

Answer 2

A species that oxidises another species by removing one or more electrons.
When an oxidising agent reacts it gains electrons and is therefore, reduced

Question 3

Define: reducing agent

Answer 3

A species that reduces another species by adding one or more electrons.
When an reducing agent reacts it loses electrons and is therefore, oxidised

Question 4

Define: disproportionation

Answer 4

Simultaneous oxidation and reduction of an element in a single reaction

Question 5

What is a redox reaction

Answer 5

A reaction that involves both reduction and oxidation

Question 6

Define oxidation number/state

Answer 6

The change that an ion has or the change that it would have if the species was fully ionic

Question 7

The oxidation number of fluorine is always…

Answer 7

-1

Question 8

The oxidation number of hydrogen is +1 except when…

Answer 8

Combined with a less electronegative element. Then it becomes -1

Question 9

The oxidation number of oxygen is always -2 except in…

Answer 9

Peroxides where it is -1 and when combined with fluorine it is +1

Question 10

The oxidation number of an uncombined element is always…

Answer 10

0

Question 11

The more negative oxidation number is always given to the…

Answer 11

More electronegative element in a substance

Question 12

If the oxidation number of an element Increases is the element oxidised or reduced?

Answer 12

OxIdised

Question 13

If the oxidation number of an element Decreases is the element oxidised or reduced?

Answer 13

ReDuced

Question 14

What does systematic naming refer to?

Answer 14

When an element can have more than one oxidation state the names of its compounds and its ions often include the oxidation number of that element
eg. FeCl2 = iron (II) chloride (oxidation number of Fe= +2)
FeCl3 = iron (III) chloride (oxidation number of Fe= +3)

Question 15

Deduce the formula for iron(III) sulfate

Answer 15

The formula of the iron(III) ion is Fe3+
The formula for the sulphate ion is SO4 2-
So the two ions are present in a 2:3 ratio to give a neutral compound giving the formula Fe2(SO4)3

Question 16

What steps must be taken when writing redox ionic equations

Answer 16

Write a balanced equation for the species
Work out the ‘before’ and ‘after’ oxidation states
Balance oxidation states with electrons
If charges don’t balance add H+ ions to one of the sides to balance
If still not balanced add enough H2O to one side so it balances