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Equilibrium and Spontaneity. Cathy Little. Jeff Bitton. Jesus 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.
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Equilibrium and Spontaneity Cathy Little Jeff Bitton Jesus 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 DHo, DSo and DGo.
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 The unit includes an introduction of topics through a series of demonstrations/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.
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 Ksp for Borax at various temperatures using titration and create a graph of -LnKsp vs. 1/T. • Students will use the graph to calculate DHo, DSo, DGo.
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 DHo, DSo, DGo.
Samples of Student work Table I – simulation lab
Samples of Student Work Table II
Samples of Student Work Table III G0 = -RTLnK or G0 = H0 - TS0 ; where R = 1
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