Writing Equilibrium Constant Expressions

Evaluation/Assessment: 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? Balanced

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 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 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 product- favored at equilibrium 2 NO2(g)  N2O4(g) Keq = 2.15 x 102 Product-favored

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