Determination of the Thermodynamic
Parameters for the Solvation of Borax
We were able to calculate the thermodynamic parameters of the borax reaction by titrating the borate
with HCL that we prepared. By calculating the concentration of the Borate Ion from our titrations, it was
possible to calculate the concentration of the sodium ion as well. By using these values, calculations
could be made for G, S, H, and Ksp for the two different temperatures.
In this lab, we will calculate the Gibb’s free energy change, enthalpy change, and the entropy change for
the dissolution of borax in water. We will find these thermodynamic parameters by standardizing a HCl
solution and titrating the borate ion with the HCl solution.
BO(OH)2-(aq) + 2 HCl(aq) + 3 HO 4 HBO(aq) + 2 Cl-(aq)
By doing this we should be able to find the Borate ion concentration which will allow us to calculate the
Ksp of the solution and use it to determine the thermodynamic parameters in this experiment.
Prepare 2 500 mL Erlenmeyer flask of borax solutions
Leave one to set at room temperature and stir for 30 min and the other in an ice bath and stir for
Determine if solution is saturated and set aside
Prepare HCl solution in a 400 mL flask
Dissolve Anhydrous Primary Std. Grade Sodium in 50 mL of water
Titrate the HCl into the Anhydrous Primary Std. Grade Sodium solution until indicator hit the
yellow-green end point
Repeat titration three times
Record the temperature of the borax solutions , and decant 60 mL of the solution in to a becaker
Take 10 mL of the borax decant and mix with 20 mL of water
Then titrate the HCl solution into the borax decant solution to the yellow-green endpoint.
Repeat the titration 3 times for each of the borax solution : room temperature and ice water bath.
Temperature (K) Ksp G
277.5 1.863E-5 25.11kJ 41.06kJ 57.47
299 6.702E-5 22.16kJ 41.06kJ 63.14
Post Lab Questions:
1. Is this Reaction Endothermic or Exothermic? Is it Enthapically favorable? Does this agree with your
expectations? (See Pre-Lab Question 1.) Explain any discrepancies.
This reaction is endothermic and enthapically favored. These are the same results as our pre-lab
2. Is this reaction Entropically favorable? Does this agree with your expectations? Explain any
The reaction is not entropically favored, which agrees with our assumptions.
3. Identify the Boron atoms in the Borate Ion pictured below. What is the geometry about each Boron
The boron atoms are the pink atoms. Their bonding geometry is tetrahedral.
4. The combustion of Peoxyacetone is a heatless explosive in that DH ~ 0 for the reaction:
2 C9H18O6(s) + 21 O2(g) 18 H2O(g) + 18 CO2(g)
The reaction is instead driven Entropically. Rationalize this in terms of the chemical reaction.
In this lab, we were able to calculate various thermodynamic quantities by titrating two borate solutions
at different temperatures. This worked because the borate dissolves at different quantities at different
temperatures. These thermodynamic quantities can show us the behavior of the chemical reaction at
different temperatures and its entropy and enthalpy characteristics.