Equilibrium and Spontaneity Cathy LittleJeff BittonJesus Hernandez

Introduction Topics include Equilibrium,Le Chatelier’s Principle and Gibbs Free Energy. These topics explain the factors that influence the spontaneity of chemical reactions. The unit includes demonstrations, a wet lab and a simulation lab.

Goals and Objectives Students will be able to determine relationships between equilibrium, thermodynamics and spontaneity – Students will be able to: Observe the effect of temperature change on the equilibrium according to LeChatelier’s principle. Determine if the reaction is endothermic or exothermic. Calculate the equilibrium constant at varying temperatures Plot –LnK as a function of 1/T and determine the values of  H o,  S o and  G o.

Intended Audience Second year Honors Chemistry Advanced Placement Chemistry Advanced Placement Physics B Visual Learners

Placement in the Curriculum Second semester AP or Honors Level students Students should be familiar with thermochemistry,titrations,solution chemistry, stoichiometry and kinetics. The unit can be modified for lower level students by de-emphasizing quantitative aspects and emphasizing conceptual features

Instructional Activities – Demo 1 – water tank equilibrium This activity models dynamic equilibrium. – Demo 2 - Cobalt chloride color change This activity illustrates shifts in equilibrium between different cobalt complexes. The unit includes an introduction of topics through a series of demonstrations/activities.

Instructional Activities Demo 3 – Detonation of nitrogen triiodide – Clear illustration of a reaction driven by both enthalpic and entropic processes.

Instructional Activities Wet laboratory – Students will determine the K sp for Borax at various temperatures using titration and create a graph of -LnK sp vs. 1/T. – Students will use the graph to calculate  H o,  S o,  G o.

Instructional Activities Simulation Lab – Students will determine the K for a simulated synthesis reaction at various temperatures and create a graph of -LnK vs. 1/T. – Students will use the graph to calculate  H o,  S o,  G o.

Samples of Student work Table I – simulation lab

Samples of Student Work Table II

Samples of Student Work Table III  G 0 = -RTLnK or  G 0 =  H 0 - T  S 0 ; where R = 1

Samples of Student Work

Assessments Traditional lab report for the wet lab, graded according to rubric. Lab report for simulation lab including questions embedded within the procedure. Homework assignments Unit Examination

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