7. Redox

Question 1

Define oxidation number

Answer 1

A measure of the number of electrons that an atom uses to bond with atoms of another element

Question 2

What are the general rules for assigning oxidation numbers?

Answer 2

• ox no for atoms in uncombined elements is 0
• in neutral molecules, sum of ox numbers is 0
• in ions, sum of ox numbers equals the charge on the ion
• the mower electronegative atom has a more negative ox number
• there are specific rules for specific elements that must be followed

Question 3

What is the oxidation number of hydrogen and when is the rule broken?

Answer 3

Almost always +1, except in metal hydrides, where it is -1

Question 4

What is the oxidation number of oxygen and when is the rule broken?

Answer 4

Almost always -2, except I’m peroxide’s where it’s -1, and OF2 it’s +2

Question 5

What is the oxidation number of group I elements and when is the rule broken?

Answer 5

+1

Question 6

What is the oxidation number of group II elements and when is the rule broken?

Answer 6

+2

Question 7

What is oxidation?

Answer 7

• increase in oxidation state
• addition of oxygen
• removal of hydrogen
• loss of electrons

Question 8

What is reduction?

Answer 8

• decrease in oxidation state
• removal of oxygen
• addition of hydrogen
• gain of electrons

Question 9

Define redox

Answer 9

Oxidation and reduction occurring in the same reaction

Question 10

Define oxidising agent/oxidant

Answer 10

Electron acceptor - it itself reduced

Question 11

Define reducing agent/reductant

Answer 11

Electron donor - it itself is oxidised

Question 12

Define disproportionation

Answer 12

Oxidation and reduction of the same element in the same reaction

Question 13

Give examples of disproportionation

Answer 13

H20 + Cl2 > HCl + HOCl

2NaOH + Cl2 > NaCl + NaClO + H2O