This document describes a virtual lab experiment to estimate the equilibrium constant, Gibbs free energy, enthalpy and entropy of cobalt chloride solutions at different temperatures. Students are instructed to use an online simulation to collect concentration and equilibrium constant data for cobalt chloride solutions at 25°C, 50°C, and 75°C. They then calculate additional thermodynamic values like Gibbs free energy, enthalpy and entropy using the collected data and appropriate equations like Cramer's rule and van't Hoff analysis. The goal is to determine these important thermodynamic properties of the cobalt chloride system at varying temperatures.

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L503 Lab Virtual SJBoylan April 2020
Introduction – In this lab you will use the virtual lab to estimate the equilibrium constant, Gibbs free
energy, enthalpy and entropy of a solution of cobalt chloride.
Procedure
1. Go to http://chemcollective.org/vlab/vlab.php
2. Click on File
3. Click on Load an Assignment
4. Click on Chemical Equilibrium (2)
5. Click on Cobalt Lab Arrow
6. Click on Cobalt(II) Chloride Exp Solutions
7. Click on 1 M CoCl2 to place an Erlenmeyer flask on the work bench.
8. Place three 1 M CoCl2 Erlenmeyer flask on the work bench.
9. Leave the first temperature at 25C
10. Right click on the second Erlenmeyer flask. Click on Thermal properties. Add check mark to
Insulated from surroundings. Enter temperature as 50. Click OK. The second Erlenmeyer flask should
now have a Temperature of 50.00 C.
11. Right click on the third Erlenmeyer flask. Click on Thermal properties. Add check mark to
Insulated from surroundings. Enter temperature as 75. Click OK. The third Erlenmeyer flask should
now have a Temperature of 75.00 C.
12. Your work bench should look like this. Additions screenshots are shown in the appendix.

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13. For each of the Erlenmeyer flask record the following items from the information list
Case 1 Case 2 Case 3
Species
A Co(H2O)6 2+
B Cl -
C CoCl4 2-
D Temperature C
pH
E Temperature K
D + 273.15 => E
E1 E2 E3
F Equilibrium Constant
C /(A C^4) => F
G Gibbs Free Energy
- 8.31 / 1000 x E ln(F) => G
G1 G2 G3
H. Enthalpy H
I. Entropy I
14. Calculate the Temperature Kelvin Absolute
D + 273.15 => E
15. Calculate the Equilibrium Constant
C /(A C^4) => F
16. Calculate the Gibbs Free Energy
- 8.31 / 1000 x E ln(F) => G
17. Use Cramers rule to calculate the enthalpy
(1x G1 - 1x G3) / (1x(-E1) - 1x(E3)) => H

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18. Use Cramers rule to calculate the entropy
(G3x(-E1) - G1x(-E3) / (1x(-E1) - 1x(E3)) => I
19. Use the van’t Hoff equation two point form to calculate the enthalpy
ln(K3 / K1) = (delta H / R)x (1/T1 - 1/T3)
delta H = 8.31/1000 x ln(K3 / K1) / (1/T1 - 1/T3)
20. The reaction is
Co(H2O)6 2+ (aq) + 4 Cl- (aq) < == > CoCl4 2- (aq) + 6 H2O
21. The equilibrium expression is
Kcomplex ion = [CoCl4 2-] / ( [Co(H2O)6 2+} x [Cl-]^4)

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Appendix Virtual Lab Screen Shots
A. Case One 25 C

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B. Case Two 50 C

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C. Case Three 75 C

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D. Summary of all data