Equilibrium Constants and Expressions

This tutorial covers the concept of chemical equilibrium and how to write equilibrium constant expressions. It explains the law of mass action and the significance of equilibrium constants, denoted as K, Kc, and Kp. The video provides examples of writing equilibrium expressions for various reactions, discusses homogeneous and heterogeneous equilibria, and explains why pure solids and liquids are excluded from these expressions. The tutorial concludes with final examples and a preview of future topics.

What is the condition for a chemical reaction to be at equilibrium?

• The concentration of reactants is zero.

• The rate of the forward reaction equals the rate of the reverse reaction.

• The pressure of the system is constant.

• The temperature of the system is constant.

What does the equilibrium constant expression represent?

• The pressure of the system.

• The temperature at which the reaction occurs.

• The relationship between the concentrations of reactants and products at equilibrium.

• The speed of the reaction.

In an equilibrium constant expression, what do the exponents represent?

• The coefficients from the balanced chemical equation.

• The speed of the reaction.

• The pressure of the system.

• The temperature of the reaction.

How is the equilibrium constant expressed when all reactants and products are gases?

• As Kd, using density.

• As Kc, using molarity.

• As Kp, using partial pressures.

• As Kt, using temperature.

What is the equilibrium constant expression for the reaction: N2 + 3H2 ⇌ 2NH3?

• [NH3] / ([N2]^2[H2]^3)

• [N2]^2[H2]^3 / [NH3]

• [N2][H2]^3 / [NH3]^2

• [NH3]^2 / ([N2][H2]^3)

What does the equilibrium constant depend on?

• The volume of the container.

• The initial concentrations of reactants.

• The stoichiometry of the reaction.

• The reaction mechanism.

In a homogeneous equilibrium, what is true about the phases of reactants and products?

• They are in different phases.

• They are all in the same phase.

• They are all solids.

• They are all liquids.

Why are pure solids and liquids not included in equilibrium constant expressions?

• They do not affect the reaction rate.

• They are not present in the reaction.

• They have no volume.

• Their concentrations are constant.

In a heterogeneous equilibrium, which components are included in the equilibrium expression?

• All components regardless of phase.

• Only liquids.

• Only solids.

• Only gases and aqueous solutions.

What is the equilibrium expression for the dissolution of lead chloride in water?

• [Pb^2+][Cl^-]^2

• [Pb^2+][Cl^-]

• [PbCl2]

• [Pb^2+]/[Cl^-]^2