Chapter 18, Problem 3STP

Interpretation Introduction

Interpretation: The oxygen−reduction reaction needs to be identified.

Concept introduction: Oxidation state is the concept which explains the gain or loss of electrons in oxidation−reduction reactions.

Answer to Problem 3STP

Correct option is C.

Explanation of Solution

C.

The given reaction is as follows:

  $\text{HCl}\left(aq\right)+\text{NaOH}\left(aq\right)\to \text{NaCl}\left(aq\right)+{\text{H}}_{\text{2}}\text{O}\left(l\right)$

In this reaction, there is no change in oxidation states of any element. Thus this reaction is not an oxidation-reduction reaction.

Conclusion

A. $\text{2Al}\left(s\right)+3{\text{I}}_{\text{2}}\left(s\right)\to 2{\text{AlI}}_{\text{3}}\left(s\right)$

In this reaction, oxidation state of aluminum increases and oxidation state of iodine decreases. Iodine is reduced and aluminium is oxidized. Thus this is an oxidation reduction reaction.

B. $\text{Mg}\left(s\right)+\text{2HCl}\left(s\right)\to {\text{MgCl}}_2\left(aq\right)+{\text{H}}_{\text{2}}\left(g\right)$

In this reaction, oxidation state of magnesium increases and oxidation state of hydrogen decreases. Hydrogen is reduced and magnesium is oxidized. Thus, this is an oxidation reduction reaction.

D. ${\text{CH}}_{\text{4}}\left(g\right)+{\text{2O}}_{\text{2}}\left(g\right)\to {\text{CO}}_2\left(g\right)+{\text{H}}_{\text{2}}\text{O}\left(l\right)$

In this reaction, oxidation state of carbon increases and oxidation state of oxygen decreases. Oxygen is reduced and carbon is oxidized. Thus this is an oxidation reduction reaction.