3.1.7 Oxidation, reduction and redox equations

Question 1

What is an oxidation reaction?

Answer 1

The gaining of oxygen

The loss of electrons

Question 2

What is a reduction reaction?

Answer 2

The removal of oxygen

The gain of electrons

Question 3

What is a redox reaction?

Answer 3

A reaction where oxidation and reduction takes place at once

Question 4

What is an oxidation state?

Answer 4

Also called oxidation numbers

Used to see what has been oxidised (lost electrons) or reduced (gained electrons) in a redox reaction

Question 5

What are the rules for oxidation states?

Answer 5

1. Every element in its uncombined state has an oxidation state of zero
2. Some elements always have the same oxidation state in all their compounds- others usually do
3. The sum of the oxidation states in a compound is zero
4. The sum of the oxidation states equals the ion charge
5. In a compound the most electronegative element always has a negative oxidation state

Question 6

What are half equations?

Answer 6

They are equations which seperate oxidation and reduction into two equations
This shows two simpler reactions

Question 7

How can half equations be combined?

Answer 7

They can be recombined to show both sides of the full redox equation
The electrons must cancel out so that the number lost equals the number gained

Question 8

What is the rule for the oxidation state for compounds?

Answer 8

The oxidation state of an atom corresponds to the number of electrons from that atom which are shared in covalent bonds

Question 9

What are the steps of redox reactions?

Answer 9

1. Write down the oxidation states of every reactant and product
2. Label if each reactant/product is oxidised/reduced
3. Balanced the number of electrons that are transferred and overall balance the redox process

Question 10

What is the oxidation state of fluorine in a compound?

Answer 10

-1

Question 11

What is the oxidation state of oxygen in a compound?

Answer 11

-2 except in peroxides where it is -1 and OF2 where it is +2

Question 12

What is the oxidation state of hydrogen in a compound?

Answer 12

+1 except in metal hydrides where it is -1

Question 13

What are the oxidation rules of aluminium?

Answer 13

Always +3

Question 14

What are the oxidation rules of chlorine?

Answer 14

-1 except in compounds with fluorine and oxygen where it is positive

Question 15

What is the formula and charge on ammonium?

Answer 15

NH4, +1

Question 16

What is the formula and charge on a carbonate ion?

Answer 16

CO3, -2

Question 17

What is the formula and charge on a nitrate ion?

Answer 17

NO3, -1

Question 18

What is the formula and charge on a sulfate ion?

Answer 18

SO4, -2

Question 19

What is the charge of silver ions?

Answer 19

+1

Question 20

What is the charge of zinc ions?

Answer 20

2+

Question 21

What is the charge and formula of a hydrogencarbonate ion?

Answer 21

HCO3 with a charge of - 1