Topic 8A Redox Chemistry

Question 1

Define the term oxidation number.

Answer 1

The charge an ion has, or the charge it would have if the species were fully ionic.

Question 2

What are the rules for assigning oxidation numbers?

Answer 2

1. The oxidation number for any uncombined element is zero.
2. The sum of oxidation numbers of all elements in a species is equal to the net charge on the species.
3. The more electronegative element in a substance is given a negative oxidation number.
4. The oxidation number of fluorine is always negative one.
5. The oxidation number of is +1, except when combined with a less electronegative element, where it becomes -1.
6. The oxidation number of oxygen is -2, except in peroxides where it is -1, and when combined with fluorine where it is +2.

Question 3

Describe oxidation and reduction in terms of electron transfer.

Answer 3

Oxidation is the loss of electrons and reduction is the gain of electrons.
OIL RIG.

Question 4

Describe oxidising and reducing agents in terms of electron transfer.

Answer 4

Oxidising agents accept electrons and are reduced.

Reducing agents donate electrons and are oxidised.

Question 5

Define the term disproportionation reaction.

Answer 5

A reaction involving the simultaneous oxidation and reduction of an element in a single species.

Question 6

How are oxidation numbers are useful concept?

Answer 6

They are useful to classify reactions as redox and disproportionation.

Question 7

How do metals and non-metals form ions?

Answer 7

Metals, in general, form positive ions by a loss of electrons with an increase in oxidation number.

Non-metals, in general, form negative ions by a gain of electrons with a decrease in oxidation number.

Question 8

The most important thing when combining ionic half-equations.

Answer 8

Making sure the number of electrons in each equation is equal.