Reduction Half Reactions

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Questions and Answers

What is the primary function of an oxidizing agent in a reduction half reaction?

To inhibit the reaction and prevent electron transfer

To gain electrons and become reduced

To lose electrons and become oxidized

To facilitate the transfer of electrons from another species (correct)

Which of the following statements is true about the organization of the reduction half reaction table?

The strongest reducing agents are listed at the bottom right corner (correct)

The weakest oxidizing agents are listed at the bottom left corner

The weakest reducing agents are listed at the top right corner

The strongest oxidizing agents are listed at the top left corner

What determines whether a reaction is spontaneous or non-spontaneous?

The presence of a reducing agent

The combination of a reduction half reaction and an oxidation half reaction

The presence of an oxidizing agent

The relative reactivity of the species involved (correct)

What is the oxidizing agent in the reaction: Cu(s) / H +(aq) / NO3–(aq) / H2O(l)?

NO3–(aq) Signup and view all the answers

What is the net result of combining a reduction half reaction and an oxidation half reaction?

A redox reaction Signup and view all the answers

Which species loses electrons in the reaction Pb(s) + 2 Ag+(aq) → 2 Ag(s) + Pb2+(aq)?

Pb(s) Signup and view all the answers

In a redox reaction, what is the purpose of multiplying the half-reactions by simple whole numbers?

To balance the electrons lost and gained Signup and view all the answers

What is the oxidation half reaction for the reaction Pb(s) + 2 Ag+(aq) → 2 Ag(s) + Pb2+(aq)?

Pb(s) → Pb2+(aq) + 2e– Signup and view all the answers

What is the reduction half-reaction in the reaction: O2(g) + 4 H +(aq) + 4e – → 2 H2O(l)?

O2(g) + 4e – → 2 H2O(l) Signup and view all the answers

What is the net ionic equation for the reaction: Fe(s) / H2O(l) / H +(aq) / O2(g)?

O2(g) + 4 H +(aq) + 2 Fe(s) → 2 H2O(l) + 2 Fe2+(aq) Signup and view all the answers

Why does a strip of zinc react with a solution of copper(II) nitrate, but a strip of copper does not react with a solution of zinc nitrate?

Because zinc is more reactive than copper Signup and view all the answers

Which of the following is a characteristic of a spontaneous redox reaction?

The reaction is exothermic Signup and view all the answers

What is the purpose of the reduction half reaction table?

To organize and compare the reactivity of various oxidizing agents Signup and view all the answers

What is the role of the species being oxidized in a redox reaction?

To lose electrons Signup and view all the answers

Which of the following species is most likely to be a reducing agent in a reaction?

E(s) Signup and view all the answers

What is the purpose of constructing half-reactions in predicting balanced redox equations?

To facilitate electron transfer Signup and view all the answers

In a disproportionation reaction, what happens to the species being reacted?

It is both oxidized and reduced Signup and view all the answers

What determines the spontaneity of a redox reaction?

The position of the oxidizing agent and reducing agent on the reductions table Signup and view all the answers

What is the purpose of a reductions table in redox reactions?

To identify the oxidizing and reducing agents in a reaction Signup and view all the answers

When creating a net ionic equation, what is the first step?

Identify all species present Signup and view all the answers

Which of the following is an example of an oxidation half reaction?

Sn(s) → Sn2+(aq) + 2e– Signup and view all the answers

What is the relationship between the position of an oxidizing agent on the reductions table and its reactivity?

The higher the position, the more reactive the OA Signup and view all the answers

What is necessary for a redox reaction to occur?

An OA must react with a RA Signup and view all the answers

Which of the following is an example of a spontaneous redox reaction?

A reaction in which the OA is positioned higher on the table than the RA Signup and view all the answers

Study Notes

Using the Reductions Table

A reduction half-reaction table shows all reactions with electrons being gained, and the species gaining electrons is the oxidizing agent.
If the table were written in reverse, it would show a loss of electrons and be called an oxidation half-reaction table.

Reduction and Oxidation Half-Reactions

In a reduction half-reaction, electrons are gained, and the species gaining electrons is the oxidizing agent.
In an oxidation half-reaction, electrons are lost, and the species losing electrons is the reducing agent.

Characteristics of the Reductions Table

The most reactive or strongest oxidizing agents are found at the upper left corner of the table.
The most reactive or strongest reducing agents are found at the lower right side of the table.
When a reduction half-reaction is added to an oxidation half-reaction, a REDOX (reduction-oxidation) reaction is formed.

Determining Spontaneous or Non-Spontaneous Reactions

A reaction is spontaneous if an oxidizing agent (OA) reacts with a reducing agent (RA) where the OA is positioned higher on the table than the RA.
A reaction is non-spontaneous if an OA reacts with an RA where the OA is positioned lower on the table than the RA.

Disproportionation

Disproportionation is a reaction where a species is both oxidized and reduced.
Example: Two iron(II) ions colliding in a solution, resulting in one iron(II) ion being oxidized to iron(III) and another iron(II) ion being reduced to iron(s).

Predicting Redox Reactions

Steps to predict balanced redox equations:
Start with two half-reaction equations
Balance each half-reaction equation
Multiply each half-reaction equation by simple whole numbers to balance electrons lost and gained
Add the two half-reaction equations, cancelling electrons and identical species

Constructing Half-Reactions

Identify all species present
Identify which species are oxidizing agents (OA) and reducing agents (RA)
Use the Reductions Table to create net ionic (redox) equations

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Description

Understanding the reduction half reaction table, where all reactions involve the gain of electrons, and how it can be reversed to show oxidation half reactions.