Equilibrium Expressions for Gases and Liquids

The video tutorial explains why the concentrations of pure solids and liquids are ignored when writing the equilibrium constant (KC) expression. It highlights that molar concentration is based on density, an intensive property, which remains constant for pure substances. Therefore, their concentrations do not change and are excluded from the KC expression. The tutorial provides examples, including reactions involving copper compounds and ethyl acetate, to illustrate these concepts.

Why are solids and pure liquids often ignored in equilibrium constant expressions?

• They react too quickly.

• Their concentrations are constant.

• They have variable concentrations.

• They are not part of the reaction.

What is the relationship between molarity and density for pure solids and liquids?

• Molarity changes with temperature.

• Density remains constant, affecting molarity.

• Density is an extensive property.

• Molarity is independent of density.

Why is density considered an intensive property?

• It varies with temperature.

• It depends on the shape of the container.

• It remains constant regardless of quantity.

• It changes with the amount of substance.

How does the volume change affect the concentration of pure solids and liquids?

• Concentration varies unpredictably.

• Concentration decreases with volume.

• Concentration increases with volume.

• Volume change does not affect concentration.

What happens to the mass per unit volume of pure solids and liquids when volume decreases?

• It becomes zero.

• It remains the same.

• It decreases.

• It increases.

In the example with ethyl acetate and acetic acid, why is water ignored in the KC expression?

• Water is a product.

• Water is a reactant.

• Water is a catalyst.

• Water is a pure liquid.

What is the primary reason for excluding pure liquids in equilibrium expressions?

• Their concentration is variable.

• They are always reactants.

• They are not part of the reaction.

• Their concentration is constant.

What distinguishes gaseous species in equilibrium expressions from solids and liquids?

• Gaseous species have constant density.

• Gaseous species are always reactants.

• Gaseous species do not affect equilibrium.

• Gaseous species vary in concentration.

Why should gaseous species appear in the KC expression?

• They are always products.

• Their moles per unit volume change.

• They have constant mass.

• They do not affect equilibrium.