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
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
Samples of Student Work
Table II
Measurement
1
2
3
4
5
6
K
0.30667
0.00991
0.00327
0.00228
0.00215
0.00176
1/T
LnK
5.0
2.0
1.0
0.7
0.5
0.4
[ Blue / Purple ]
K
[Re d ] *[Green]
1.18
4.61
5.72
6.08
6.14
6.34
Samples of Student Work
Table III
0
Measurement Temperature D H
1
0.2
2
0.5
3
1
4
1.5
5
2
6
2.5
DS
-1.1185
-1.1185
-1.1185
-1.1185
-1.1185
-1.1185
0
0
DG
-6.7982
-6.7982
-6.7982
-6.7982
-6.7982
-6.7982
0.2364
2.3073
5.7221
9.1272
12.286
15.857
DG0 = -RTLnK or DG0 = DH0 - TDS0 ; where R = 1
Samples of Student Work
-Lnk vs. 1/T
-Lnk = -1.1185/T + 6.7982
R2 = 0.9992
7.00
6.00
-Lnk
5.00
4.00
3.00
2.00
1.00
0.00
0.0
1.0
2.0
3.0
1/T
4.0
5.0
6.0
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
The End