Transcript Equilibrium Constants

Writing Equilibrium Constant
Expressions
 Objective:
 Today I will be able to:
 Write and solve the equilibrium constant expression for a reaction
 Determine if a reaction is reactant or product favored
 Evaluation/Assessment:
 Informal assessment: Monitoring student interactions and questions
as they complete the Equilibrium constant practice.
 Formal assessment: Analyzing student responses to the practice and
the exit ticket
 Common Core Connection
 Build Strong Content Knowledge
 Reason abstractly and quantitatively
 Make sense of problems and persevere in solving them
Lesson Sequence
 Evaluate: Warm – Up
 Engage/Explore: Writing Equilibrium Constant Expression
Inquiry
 Explain: Equilibrium Constant Notes
 Elaborate: Equilibrium Constant Practice
 Evaluate: Exit Ticket
Warm - Up
 What does it mean to achieve equilibrium?
 What are some examples of equilibrium?
Objective
 Today I will be able to:
 Write and solve the equilibrium constant expression for a
reaction
 Determine if a reaction is reactant or product favored
Homework
 Finish Equilibrium Practice Problems
 Wear Closed Toe Shoes Wednesday/ Thursday
Agenda
 Warm – Up
 Equilibrium Constant Expression Inquiry
 Equilibrium Constant Notes
 Equilibrium Constant Practice
 Exit Ticket
Writing Equilibrium Constant
Expressions
Complete the inquiry activity at your desk
Brainstorm: What does it mean to be
in equilibrium?
Chemical Reactions
 We are use to thinking about chemical reactions like this:
Chemical Reactions can be Reversible
 Some reactions are reversible, where the products can
regenerate the original reactants
Chemical Equilibrium
 The forward and reverse reaction rates are equal
 Equilibrium DOES NOT mean the concentrations of
reactants and products are equal
Dynamic Chemical Equilibrium
 Chemists refer to equilibrium as dynamic because the
reaction does not stop when it reaches equilibrium, but
becomes constant
 The system is changing but there is no net reaction
 In a closed system, almost all reactions will reach equilibrium
Equilibrium Constant Notes
Equilibrium Constant
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Expresses the relative concentrations of reactants and
products at equilibrium by using an “equilibrium
constant” – Keq
a A + b B  c C + d D
Equilibrium Constant
 Only include gases and aqueous solutions when writing
equilibrium constants
 Solids and liquids are not included
 They can be represented with a [1] or left out entirely
Types of Equilibrium Problems
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Quantitative
Keq < 1, then the reaction is reactant-favored at
equilibrium
COCl2(g)  CO(g) + Cl2(g)
Keq = 2.2 x 10-10
Reactant-favored
Types of Equilibrium Problems
Keq > 1, then the reaction is productfavored at equilibrium
 2 NO2(g)  N2O4(g)
 Keq = 2.15 x 102
 Product-favored
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Keq and Stresses on the system
 Keq does not change with change in concentration
 It will change based on change in temperature and change of
pressure
Types of Equilibrium Problems
 Quantitative (uses the Keq equation)
 Write the equilibrium expression for the following reaction
 2 SO2(g) + O2(g)  2 SO3(g)
[SO3]2
_______________
[SO2]2 [O2]
Types of Equilibrium Problems
 If .0172 M of O2, .0250 M of SO2 and .00140 M of SO3 at
equilibrium, calculate Keq
[SO3]2
_______________
[SO2]2 [O2]
[.00140]2
_______________
[.0250]2 [.0172]
Keq = .18 (reactant favored)
Equilibrium Constant Practice
Complete the practice at your desk. Whatever you
do not finish will become your homework
Exit Ticket
 Given the following reaction:
 Use Le Chatelier’s principle to determine what would
happen if the following changes were made
 Increase the concentration of N2
 Increase the concentration of NH3
 Remove NH3 from the reaction after it is made