Chapter 17, Problem 46A

Interpretation Introduction

Interpretation:

The equilibrium constant expression for a heterogeneous equation is to determined.

Concept introduction:

The equilibrium constant is the ratio of concentration of products to the concentration of reactants and heterogeneous reaction is that in which the reactants and products are present in different phases.

Answer to Problem 46A

The equilibrium expression for the given reaction is

${\text{K}}_{\text{eq}}\text{=}\left[{\text{CO}}_{\text{2}}\left(\text{g}\right)\right]$

Because given reaction is the type of heterogeneous reaction because in this reaction product and reactant are in different phases. So, the concentration of $\text{CaO}\left(\text{g}\right)$ and ${\text{CaCO}}_{\text{3}}\left(\text{g}\right)$ may be assumed to be constant or unity.

Explanation of Solution

The equilibrium constant is the ratio of concentration of products to the concentration of reactants.

A heterogeneous reaction is that in which reactants and product are in the different phases.

The given reversible reaction is

${\text{CaCO}}_{\text{3}}\left(\text{s}\right)\rightleftharpoons \text{CaO}\left(\text{s}\right){\text{+CO}}_{\text{2}}\left(\text{g}\right)$

The equilibrium expression for the given reaction is

${\text{K}}_{\text{eq}}\text{=}\frac{\left[\text{CaO}\left(\text{s}\right)\right]\left[{\text{CO}}_{\text{2}}\left(\text{g}\right)\right]}{\left[{\text{CaCO}}_{\text{3}}\left(\text{s}\right)\right]}$

The concentration of $\text{CaO}\left(\text{g}\right)$ and ${\text{CaCO}}_{\text{3}}\left(\text{g}\right)$ may be assumed to be constant or unity. So, the equilibrium constant becomes

${\text{K}}_{\text{eq}}\text{=}\left[{\text{CO}}_{\text{2}}\left(\text{g}\right)\right]$

Reason: Heterogeneous reaction does not include the concentration of pure solids and pure liquids because their concentration remains constant.

Conclusion

The equilibrium expression for the given reaction is

${\text{K}}_{\text{eq}}\text{=}\left[{\text{CO}}_{\text{2}}\left(\text{g}\right)\right]$

Because given reaction is the type of heterogeneous reaction because in this reaction product and reactant are in different phases. So, the concentration of $\text{CaO}\left(\text{g}\right)$ and ${\text{CaCO}}_{\text{3}}\left(\text{g}\right)$ may be assumed to be constant or unity.