Kc and Kp ConversionsHess’s Law in Equilibrium Constants

• Today I will be able to:– Convert between Kp and Kc– Apply Hess’s Law to calculating equilibrium

constants• Informal assessment – monitoring student

interactions as they complete the practice problems

• Formal assessment – analyzing responses to the practice prblems

Lesson Sequence

• Evaluate: Warm Up• Explain: Notes• Explore: Webquest• Elaborate: Practice Problems• Evaluate: Closure

Warm Up

Objectives

• Today I will be able to:– Convert between Kp and Kc– Apply Hess’s Law to calculating equilibrium

constants

Homework

• Continue working practice problems and reading chapter 5

Agenda

• Warm Up• Notes• Webquest• Practice Problems• Closure

Equilibrium Constants and Hess’s Law Notes

Manipulating Equilibrium ConstantsThe equilibrium constant of a reaction in the reverse reaction is the reciprocal of the equilibrium constant of the forward reaction.

Manipulating Equilibrium ConstantsThe equilibrium constant of a reaction that has been multiplied by a number is the equilibrium constant raised to a power that is equal to that number.

Manipulating Equilibrium ConstantsThe equilibrium constant for a net reaction made up of two or more steps can be found from the equilibrium constants for the individual steps.`

At 1565 K we have these equilibrium constants:

Example Problem 1

Answer Problem 1

Example Problem 2

Answer Problem 2

Relationship between Kp and Kc

Visit the website below to find notes and examples

http://www.chem.purdue.edu/gchelp/howtosolveit/

Relationship between Kc and Kp

Substituting P=[A]RT into the expression for Kp for each substance, the relationship between Kc and Kp becomes

Where:

Kp = Kc (RT)n

n = (moles of gaseous product) – (moles of gaseous reactant)

Hint: ‘products–reactants’ and ‘products over reactants’ is a common theme in chemistry.

Practice Problems

Closure – Practice Problems

• Using the 10th edition of the textbook• Equilibrium; the Equilibrium Constant

14, 15, 19, 21, 22, 24• Calculating Equilibrium Constants

28-30, 31-33• Applications of Equilibrium Constants

37-38, 41-44, 49

Closure – Practice Problems

• Using the 15th edition of the textbook• Equilibrium; the Equilibrium Constant15,17,21,23,25,27,28• Calculating Equilibrium Constants

31-33, 35-37• Applications of Equilibrium Constants 43-

45, 41-44, 47, 49, 51