Chapter 9, Problem 138A

Interpretation Introduction

Interpretation:

The given chemical equation needs to be completed and whether a precipitate forms or not needs to be determined.

$\text{Mg}\left(\text{s}\right)\text{+NaOH}\left(\text{aq}\right)\to$

Concept introduction:

If two solutions are mixed, the ions in the resulting solution may react with each other. A double displacement reaction may take place. This can result in the formation of a precipitate, water and gas.

Answer to Problem 138A

The reaction occurs and a precipitate is formed.

$\text{Mg}\left(\text{s}\right)\text{+NaOH}\left(\text{aq}\right)\to \text{Mg}{\left(\text{OH}\right)}_{\text{2}}\left(\text{s}\right)\text{+Na}\left(s\right)$

Explanation of Solution

The first product in this reaction is sodium hydroxide and second one is Na. According to the solubility rule given in the table, hydroxides are insoluble but group 2 ions of hydroxides are slightly soluble. Hence, the possible products formed in the given reaction are given below.

$\text{Mg}\left(\text{s}\right)\text{+NaOH}\left(\text{aq}\right)\to \text{Mg}{\left(\text{OH}\right)}_{\text{2}}\left(\text{s}\right)\text{+Na}\left(s\right)$

Therefore, $\text{Mg}{\left(\text{OH}\right)}_{\text{2}}$ precipitate out in this reaction and reaction does occur.

Conclusion

A precipitate is formed when two soluble salts combined together and produce a solid product.