Equilibrium Expressions in Chemistry

This video tutorial explains how to write equilibrium expressions for chemical reactions. It covers the law of mass action, showing how to express the equilibrium constant (K) as the ratio of products to reactants, with coefficients as exponents. The tutorial includes examples with nitrogen and hydrogen, hydrogen and bromine, calcium carbonate decomposition, and hydrofluoric acid reactions. It emphasizes the exclusion of solids and liquids from equilibrium expressions and differentiates between Kp for gases and Kc for aqueous solutions.

What is the first step in writing an equilibrium expression for a chemical reaction?

• Calculate the reaction rate

• Identify the products and reactants

• Balance the chemical equation

• Determine the temperature

In the law of mass action, what do the coefficients in a balanced chemical equation become in the equilibrium expression?

• Subscripts

• Coefficients

• Exponents

• Constants

For the reaction of hydrogen gas with bromine, what is the coefficient of HBr in the equilibrium expression?

• 4

• 2

• 3

• 1

Why are solids and liquids excluded from equilibrium expressions?

• They are always in excess

• They have variable concentrations

• They do not affect the position of equilibrium

• They are not part of the reaction

In the decomposition of calcium carbonate, what is the equilibrium expression for the reaction?

• K = [CO2]

• K = [CaO]

• K = [CaCO3]

• K = [CaO][CO2]

When writing the equilibrium expression for a reaction involving hydrofluoric acid and hydroxide, which component is excluded?

• Water

• Fluoride

• Hydroxide

• Hydrofluoric acid

What is the equilibrium expression for the reaction between hydrofluoric acid and hydroxide?

• K = [HF]/[F-][OH-]

• K = [F-]/[HF][OH-]

• K = [F-]

• K = [HF][OH-]

What is the role of the equilibrium constant (K) in a chemical reaction?

• It calculates the pressure of the system

• It measures the temperature of the reaction

• It indicates the ratio of products to reactants at equilibrium

• It determines the speed of the reaction

Which phase of substances is considered in the equilibrium expression?

• Liquid

• Solid

• Gas

• All phases

What is the significance of using Kp and Kc in equilibrium expressions?

• Kp is for aqueous solutions, Kc is for solids

• Kp is for liquids, Kc is for gases

• Kp is for gases, Kc is for aqueous solutions

• Kp is for solids, Kc is for liquids