Redox

Question 1

OXIDATION

Answer 1

• Loss of electrons
• When the oxidation state increases

Question 2

REDUCTION

Answer 2

• Gain of electrons
• When the oxidation state decreases

Question 3

Oxidising Agent

Answer 3

• gains e- from the other species
• oxidising agent is itself reduced

Question 4

Reducing Agent

Answer 4

• loses e- to give to other species
• reducing agent is itself oxidised

Question 5

Definition of oxidation state

Answer 5

The number assigned to atoms in a compound to follow which elements are gaining or losing electrons in a reaction

Question 6

Oxidation states

Answer 6

Uncombined elements (e.g. Mg, Na(s), O2(g), H2(g), Cl2(g)) have an oxidation state of zero

Ag = +1
Zn= +2

** when we calculate an unknown oxidation number we must always give the answer for a single element **

Question 7

Spectator ion

Answer 7

Oxidation state remains unchanged

Question 8

Transition elements

Answer 8

A Roman numeral is used to indicate the oxidation state of the transition element

Question 9

Oxyanions

Answer 9

negative ions that contain oxygen ‘-ate’) and another element, e.g. sulfate, SO42-,

Question 10

Balancing half equations

Answer 10

1. Balance for the central ion/atom (this is not O or H)
2. Balance for the O present by adding water molecules
3. Balance for the H by adding H+ ions
4. Balance for the charges by adding electrons

Question 11

Disproportionation

Answer 11

The same atom undergoes oxidation and reduction at the same time.