Explain why pure liquids and solids can be ignored while writing the equilibrium constant expression?
(N/A) For a pure substance (both solids and liquids),the concentration is defined as:
$[Pure \text{ } substance] = \frac{\text{Number of moles}}{\text{Volume}}$
$= \frac{\text{Mass} / \text{Molecular mass}}{\text{Volume}}$
$= \frac{\text{Mass}}{\text{Volume} \times \text{Molecular mass}}$
$= \frac{\text{Density}}{\text{Molecular mass}}$
Since the density and molecular mass of a pure substance are constant at a given temperature,the concentration of a pure substance is a constant value.
This constant value is incorporated into the equilibrium constant $(K_c)$,and therefore,pure solids and liquids are omitted from the equilibrium constant expression.
$[Pure \text{ } substance] = \frac{\text{Number of moles}}{\text{Volume}}$
$= \frac{\text{Mass} / \text{Molecular mass}}{\text{Volume}}$
$= \frac{\text{Mass}}{\text{Volume} \times \text{Molecular mass}}$
$= \frac{\text{Density}}{\text{Molecular mass}}$
Since the density and molecular mass of a pure substance are constant at a given temperature,the concentration of a pure substance is a constant value.
This constant value is incorporated into the equilibrium constant $(K_c)$,and therefore,pure solids and liquids are omitted from the equilibrium constant expression.
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