Oxidising and reducing agents

Table of Contents

1. Oxidising agents and reducing agents
2. Redox reactions
   1. Oxidation numbers
3. Oxidising agents and reducing agents
   1. Oxidants and reductants
   2. Common oxidants and reductants
4. Half-equations
   1. Writing half-equations
   2. Combining half-equations
5. Reduction potentials
   1. Source of reduction potentials
   2. Using standard electrode potentials
   3. Predicting reaction tendencies
6. Redox reactions in action

1. Additional resources:
   1. Glossary
   2. Print content

Oxidants and reductants

In the activity below, identify the oxidant and/or the reductant in each case. To do this you can either use the concept of oxidation number or the transfer of electrons to determine which substances are being reduced or oxidised. Make sure that you read all the feedback in the activities.

Activity: Oxidants and reductants

1

Burning magnesium Which substance is acting as the oxidant in the following reaction? 2 Mg + O2 → 2 MgO a) magnesium b) oxygen Correct, the oxygen is gaining electrons as it is reduced from O2 to oxide ions (O2-) Incorrect, the oxidation number for oxygen reduces from zero in O2 to negative two in (O2-).Your answer has been saved.

2

Extraction of iron from iron ore Which substance is acting as the reductant in the following reaction? 2 Fe2O3 + 3 CO → 4 Fe + 3 CO2 a) iron b) oxygen c) carbon monoxide Correct, the carbon monoxide is gaining oxygen, or the oxidation number of carbon is increasing from +2 in CO to +4 in CO2.Incorrect, the oxidation number of carbon is increasing from +2 in CO to +4 in CO2.Your answer has been saved.

3

Dilute acid reacting with magnesium Which 'part' of the acid is acting as the oxidant in the following reaction? Mg + 2 HCl → MgCl2 + H2 a) hydrogen ion b) chloride ion Correct, the oxidation number of hydrogen is increasing from +1 in H+ to zero in H2.Incorrect, hydrogen is being reduced.Your answer has been saved.

4

Testing sulfur dioxide content in wine Which substance is acting as the oxidant in this reaction? SO2 + 2 H2O + I2 → 2 I- + 4 H+ + SO42- a) SO2 b) H2O c) I2 Correct, the oxidation number of iodine is reducing from zero in I2 to negative one in (I-).Incorrect, the iodine is being reduced from iodine (I2) to iodide (I-).Your answer has been saved.