Chemistry: What Oxidation and Reduction Mean in Redox Reactions (OIL RIG) Practice
Identify electron loss, electron gain, oxidizing agents, and reducing agents
Chemistry: What Oxidation and Reduction Mean in Redox Reactions (OIL RIG) Practice
Identify electron loss, electron gain, oxidizing agents, and reducing agents
Chemistry - Grade 9-12
- 1
In your own words, explain what OIL RIG means in chemistry.
Focus on what happens to electrons, not oxygen.
OIL RIG means Oxidation Is Loss of electrons and Reduction Is Gain of electrons. A substance that loses electrons is oxidized, and a substance that gains electrons is reduced. - 2
Magnesium reacts with oxygen to form magnesium oxide: 2Mg + O2 -> 2MgO. In this reaction, magnesium atoms become Mg2+ ions. Is magnesium oxidized or reduced? Explain.
Magnesium is oxidized because each magnesium atom loses two electrons to form Mg2+. Losing electrons is oxidation. - 3
Chlorine reacts with sodium to form sodium chloride: 2Na + Cl2 -> 2NaCl. Each chlorine atom becomes Cl- in the product. Is chlorine oxidized or reduced? Explain.
A negative ion usually forms when an atom gains electrons.
Chlorine is reduced because each chlorine atom gains one electron to form Cl-. Gaining electrons is reduction. - 4
In the reaction Zn + Cu2+ -> Zn2+ + Cu, identify the substance that is oxidized and the substance that is reduced.
Zinc is oxidized because Zn loses two electrons to become Zn2+. Copper(II) ion is reduced because Cu2+ gains two electrons to become Cu. - 5
For the half-reaction Fe2+ -> Fe3+ + e-, state whether iron is oxidized or reduced, and explain how you know.
When electrons are products, the substance has lost electrons.
Iron is oxidized because Fe2+ loses one electron to become Fe3+. The electron appears on the product side, showing electron loss. - 6
For the half-reaction Ag+ + e- -> Ag, state whether silver is oxidized or reduced, and explain how you know.
Silver is reduced because Ag+ gains one electron to become neutral Ag. The electron appears on the reactant side, showing electron gain. - 7
In the reaction 2Al + 3Cu2+ -> 2Al3+ + 3Cu, which reactant is the reducing agent? Explain.
The reducing agent is the substance that gets oxidized.
Aluminum is the reducing agent because Al loses electrons and is oxidized. The reducing agent causes another substance, Cu2+, to be reduced. - 8
In the reaction 2Al + 3Cu2+ -> 2Al3+ + 3Cu, which reactant is the oxidizing agent? Explain.
Copper(II) ion is the oxidizing agent because Cu2+ gains electrons and is reduced. The oxidizing agent causes another substance, Al, to be oxidized. - 9
Assign oxidation numbers to sulfur in H2S and in S. Then decide whether sulfur is oxidized or reduced in the change H2S -> S.
An increase in oxidation number means oxidation.
In H2S, sulfur has an oxidation number of -2 because hydrogen is usually +1. In elemental sulfur, S has an oxidation number of 0. Sulfur is oxidized because its oxidation number increases from -2 to 0. - 10
Assign oxidation numbers to manganese in MnO4- and Mn2+. Then decide whether manganese is oxidized or reduced in the change MnO4- -> Mn2+.
Oxygen is usually -2, and the oxidation numbers must add up to the ion charge.
In MnO4-, manganese has an oxidation number of +7 because four oxygens contribute -8 and the total charge is -1. In Mn2+, manganese has an oxidation number of +2. Manganese is reduced because its oxidation number decreases from +7 to +2. - 11
A student says, "Oxidation always means a substance gains oxygen." Explain why this statement is incomplete or misleading.
The statement is incomplete because oxidation is defined as loss of electrons. Some oxidations involve gaining oxygen, but many redox reactions can be explained by electron transfer even when oxygen is not involved. - 12
Consider the reaction 2K + Br2 -> 2KBr. Potassium becomes K+ and bromine becomes Br-. Identify what is oxidized, what is reduced, the reducing agent, and the oxidizing agent.
The substance oxidized is the reducing agent, and the substance reduced is the oxidizing agent.
Potassium is oxidized because K loses one electron to form K+. Bromine is reduced because Br gains one electron to form Br-. Potassium is the reducing agent, and bromine is the oxidizing agent.