Chapter 23, Problem 82A

Interpretation Introduction

Interpretation: To determine the better product among the anhydrous and the decahydrate compounds.

Concept Introduction: Anhydrous compounds are those compounds that do not contain any water element in it. These are the crystalline substances in which water has been removed by a process called crystallization. Whereas decahydrate compounds will contain10 molecules of water in it. This water is present in the combined form.

Answer to Problem 82A

Anhydrous compound ${\text{Na}}_{\text{2}}{\text{CO}}_{\text{3}}(s)$ is better than decahydrate compound ${\text{Na}}_{\text{2}}{\text{CO}}_{\text{3}}.{\text{10H}}_{\text{2}}\text{O}(s)$

Explanation of Solution

Anhydrous compounds will not contain water molecules in them. Hence, they exist as a pure form of a compound. In this case, ${\text{Na}}_{\text{2}}{\text{CO}}_{\text{3}}(s)$ is the pure form of the compound. These anhydrous compounds are used in reactions where no water is required and also can be used for general chemical reactions. Hydrated compounds such as ${\text{Na}}_{\text{2}}{\text{CO}}_{\text{3}}.{\text{10H}}_{\text{2}}\text{O}(s)$ contain water molecules in them. These compounds cannot be used in a reaction where no water should be involved. These hydrated compounds will affect the solubility and stability of the compound. Therefore, anhydrous compounds are mostly used.

Conclusion

Anhydrous forms are the most stable forms of the compounds while the hydrated forms will affect the stability of the compound. In hydrated molecules, water combines in different proportions and these water molecules will surround and interact with the solute molecule or ion. Hence not used in all the reactions as they may affect the stability.