Equilibrium and SpontaneityEquilibrium and Spontaneity

                                                                     

                              

Cathy Little Jeff Bitton Jesus Hernandez

IntroductionIntroduction

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 ObjectivesGoals 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

Ho, So and Go.

Intended AudienceIntended Audience

Second year Honors Chemistry

Advanced Placement Chemistry

Advanced Placement Physics B

Visual Learners

Placement in the CurriculumPlacement 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 ActivitiesInstructional 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 Instructional Activities

Demo 3 – Detonation of nitrogen triiodide– Clear illustration of a reaction driven by both

enthalpic and entropic processes.

Instructional ActivitiesInstructional 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 Ho, So, Go.

Instructional ActivitiesInstructional 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 Ho, So, Go.

Samples of Student workSamples of Student work

Measurement Temperature # Blue/Purple # Red # Green

1 0.2 460 50 30

2 0.5 320 190 170

3 1 233 277 257

4 1.5 202 308 288

5 2 197 313 293

Table I – simulation lab

Samples of Student WorkSamples of Student Work

Measurement K 1/T LnK1 0.30667 5.0 1.182 0.00991 2.0 4.613 0.00327 1.0 5.724 0.00228 0.7 6.085 0.00215 0.5 6.146 0.00176 0.4 6.34

][*][Re

]/[

Greend

PurpleBlueK

Table II

Samples of Student WorkSamples of Student Work

Measurement Temperature H0 S0 G0

1 0.2 -1.1185 -6.7982 0.23642 0.5 -1.1185 -6.7982 2.30733 1 -1.1185 -6.7982 5.72214 1.5 -1.1185 -6.7982 9.12725 2 -1.1185 -6.7982 12.2866 2.5 -1.1185 -6.7982 15.857

Table III

G0 = -RTLnK or G0 = H0 - TS0 ; where R = 1

Samples of Student WorkSamples of Student Work

-Lnk vs. 1/T -Lnk = -1.1185/T + 6.7982

R2 = 0.9992

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0.0 1.0 2.0 3.0 4.0 5.0 6.0

1/T

-Ln

k

AssessmentsAssessments

Traditional lab report for the wet lab, graded according to rubric.

Lab report for simulation lab including questions embedded within the procedure.

Homework assignmentsUnit Examination

The End