Chapter 4 Redox reactions

Question 1

Conjugate redox pair

Answer 1

An oxidising agent and its corresponding reducing agent eg Cu2+/Cu.

Question 2

Oxidant/Oxidising agent

Answer 2

A chemical species (element, compound or ion) which accepts one or more electrons in an oxidation-reduction reaction. An oxidant causes another substance to be oxidized, and in the process the oxidant is reduced.

Question 3

Oxidation

Answer 3

(1) A reaction in which oxygen is a reactant. Oxidation can be defined as the addition of oxygen to form oxides, such as combustion reactions.

(2) The process by which a chemical species (element, compound, ion) loses electrons. An oxidation half-reaction will show electrons as products (on the right hand side of the arrow). Oxidation is said to have occurred when there is an increase in an element’s oxidation number during the reaction.

Question 4

Oxidation number

Answer 4

A number assigned to an atom in a compound or as a free element, which represents the charge that the atom would have if it was an ion. A series of oxidation number rules are used to determine the oxidation number of an element in a compound. Oxidation numbers are used to identify redox reaction.

Question 5

Oxidised

Answer 5

The loss of electrons or an increase in oxidation number. When a substance is oxidized, the electrons are written on the right hand side of the arrow in the half equation.

Question 6

Redox reaction

Answer 6

A reaction in which electron transfers from the reducing agent to the oxidizing agent. In a redox reaction, the oxidation number of one reactant will increase (be oxidised) and the oxidation number of another reactant will decrease (be reduced).

Question 7

Reduced

Answer 7

Gain of electrons or a decrease in oxidation number. When a substance is reduced, the electrons appear on the left hand side of the arrow in the half- equation.

Question 8

Reductant/Reducing agent

Answer 8

A reactant which causes reactant to gain electrons or for its oxidation number to decrease.
The reducing agent is, itself, oxidized and loses electrons or for its oxidation number to increase.

A reactant which causes another reactant to be reduced, and in the process it, itself, is oxidised.

Question 9

Reduction

Answer 9

The process whereby a species (element, compound, ion) gains electrons or decreases its oxidation number. A reduction half-equation will show the electrons in the left hand side of the arrow (the reactant side) in the equation.