Chapter 20.1, Problem 1SP

(a)

Interpretation Introduction

Interpretation: The oxidizing and reducing agents in the chemical reaction $2\text{Na}\left(s\right)+\text{S}\left(s\right)\to {\text{Na}}_{\text{2}}\text{S}\left(s\right)$ is to be determined.

Concept Introduction: The reaction in which oxidation and reduction take place simultaneously is a redox reaction. The process that involves the loss of electrons in a chemical reaction is referred to as oxidation. And the process that involves the gain of electrons in a chemical reaction is referred to as the reduction.

Answer to Problem 1SP

The chemical species that have undergone oxidation is sodium and that has undergone reduction is sulfur. And the oxidizing agent in the reaction is sulfur and the reducing agent is sodium.

Explanation of Solution

The chemical species which lost electrons is said to be oxidized. And the one which gains electrons is reduced. This can be identified by checking the oxidation number of each chemical species involved in the chemical reaction. The oxidation number of oxidized species is found to rise and the oxidation number of reduced species is found to be decreased.

And also the chemical species that undergo reduction is identified as the oxidizing agent while the one that undergoes oxidation is identified as the reducing agent. In the given reaction,

  $2\text{Na}\left(s\right)+\text{S}\left(s\right)\to {\text{Na}}_{\text{2}}\text{S}\left(s\right)$

The oxidation state of sodium, $\text{Na}$ is zero at the beginning and after the completion of the reaction, the oxidation number changed to $\text{+2}$ . That is, each sodium atom in ${\text{Na}}_2\text{S}$ loses one electron. While the oxidation number of sulfur is reduced to $-\text{2}$ from zero after the completion of the reaction.

Therefore, the one that undergoes oxidation is sodium and the one that undergoes reduction is sulfur.

So, the oxidizing agent is sulfur and the reducing agent is sodium.

(b)

Interpretation Introduction

Interpretation: The oxidizing and reducing agents in the chemical reaction $4\text{Al}\left(s\right)+3{\text{O}}_{\text{2}}\left(g\right)\to 2{\text{Al}}_{\text{2}}{\text{O}}_3\left(s\right)$ is to be determined.

Concept Introduction: The reaction in which oxidation and reduction take place simultaneously is a redox reaction. The process that involves the loss of electrons in a chemical reaction is referred to as oxidation. And the process that involves the gain of electrons in a chemical reaction is referred to as the reduction.

Answer to Problem 1SP

The chemical species that have undergone oxidation is aluminum and that has undergone reduction is oxygen. And the oxidizing agent in the given reaction is oxygen and the reducing agent is aluminum.

Explanation of Solution

The chemical species which lost electrons is said to be oxidized. And the one which gains electrons is reduced. This can be identified by checking the oxidation number of each chemical species involved in the chemical reaction. The oxidation number of oxidized species is found to rise and the oxidation number of reduced species is found to be decreased.

And also the chemical species that undergo reduction is identified as the oxidizing agent while the one that undergoes oxidation is identified as the reducing agent. In the given reaction,

  $4\text{Al}\left(s\right)+3{\text{O}}_{\text{2}}\left(g\right)\to 2{\text{Al}}_{\text{2}}{\text{O}}_3\left(s\right)$

The oxidation number of aluminum $\text{Al}$ has been increased from zero to $\text{+3}$ by the loss of three electrons. So, it has undergone oxidation.

While the oxidation number of oxygen has been reduced from zero to $-\text{3}$ . So, it has undergone reduction by the gain of three electrons.

So, the oxidizing agent is oxygen and the reducing agent is aluminum.