[23.1] redox reactions

Question 1

what is oxidation?

Answer 1

• increase in oxidation state
• loss of electrons

Question 2

what is reduction?

Answer 2

• decrease in oxidation state
• gain of electrons

Question 3

what is a disproportionation reaction?

Answer 3

when a single substance is both oxidised and reduced

Question 4

how can a redox reaction be shown as 2 halves?

Answer 4

• an oxidation half equation
• a reduction half equation

Question 5

how do you write a redox equation from half equations?

Answer 5

1. balance the electrons
2. add and cancel electrons
3. cancel any species that are on both sides of the equation

Question 6

how can you write a redox equation from oxidation numbers?

Answer 6

1. summarise the information provided
2. assign oxidation numbers to identify the atoms that change their oxidation number
3. balance only the species that contain elements that have changed oxidation number
4. balance any remaining atoms

Question 7

how can you predict the products of redox reactions by writing a half equation?

Answer 7

1. assign the oxidation numbers and the change in oxidation number
2. balance the electrons
3. balance any remaining atoms and predict any further species

Question 8

how do you form the equation for redox in the presence of an acid?

Answer 8

1. calculate oxidation states on each side of the equation
2. balance the element changing oxidation state
3. balance electrons
4. balance Os. for every O gained / lost, add / remove one H₂O
5. balance Hs. for every H gained / lost, add / remove one H+ ion
6. check everything is balanced