Thermodynamics Of Borax
Thermodynamics of Borax
C3C Justin Nevins
Chemistry 200, Section M1A
Introduction The purpose of the lab was to determine how the solubility of Borax (Na2B4(OH)4) and other thermodynamic quantities such as enthalpy, entropy, and Gibbs free energy depend on temperature. When Sodium borate octahydrate (Borax) dissociates in water it forms two sodium ions, one borate ion and eight water molecules. The chemical reaction is shown as:
(reaction 1)
A simple acid-base titration can be used to determine the concentration of the borate ion base. By dissolving Borax into distilled (DI) water at two different temperatures, the amount of borate that went into the solution at each temperature can be measured. The balanced equation:
(reaction 2)
represents the titration of the borax where the endpoint of the reaction is signaled by the change of bromocresol purple indicator, from purple to yellow. To understand how temperature affects thermodynamic quantities equation 1 – equation 4 shown in Appendix A were used to calculate the solubility product constant, enthalpy, entropy, and Gibbs free energy respectively. Using these equations, the aforementioned thermodynamic quantity’s dependence on temperature is more understood by the lab’s completion. Experimental Methods To start the experiment two separate titrations were set up, one at room temperature and the other in an ice bath. For the room temperature Borax titration, a saturated solution was created by adding 1.5 grams of solid Borax to 50mL of DI water and a stir bar to a beaker that was stirred for at least ten minutes. To assure that equilibrium was sustained throughout the stirring, it was stopped periodically to assure that there was solid Borax present in the beaker keeping a saturated solution. Next, a burette was filled with approximately 50mL of the .103M Hydrochloric Acid solution (HCl). For the room temperature Borax titrations the
C3C Justin Nevins
Chemistry 200, Section M1A
Introduction The purpose of the lab was to determine how the solubility of Borax (Na2B4(OH)4) and other thermodynamic quantities such as enthalpy, entropy, and Gibbs free energy depend on temperature. When Sodium borate octahydrate (Borax) dissociates in water it forms two sodium ions, one borate ion and eight water molecules. The chemical reaction is shown as:
(reaction 1)
A simple acid-base titration can be used to determine the concentration of the borate ion base. By dissolving Borax into distilled (DI) water at two different temperatures, the amount of borate that went into the solution at each temperature can be measured. The balanced equation:
(reaction 2)
represents the titration of the borax where the endpoint of the reaction is signaled by the change of bromocresol purple indicator, from purple to yellow. To understand how temperature affects thermodynamic quantities equation 1 – equation 4 shown in Appendix A were used to calculate the solubility product constant, enthalpy, entropy, and Gibbs free energy respectively. Using these equations, the aforementioned thermodynamic quantity’s dependence on temperature is more understood by the lab’s completion. Experimental Methods To start the experiment two separate titrations were set up, one at room temperature and the other in an ice bath. For the room temperature Borax titration, a saturated solution was created by adding 1.5 grams of solid Borax to 50mL of DI water and a stir bar to a beaker that was stirred for at least ten minutes. To assure that equilibrium was sustained throughout the stirring, it was stopped periodically to assure that there was solid Borax present in the beaker keeping a saturated solution. Next, a burette was filled with approximately 50mL of the .103M Hydrochloric Acid solution (HCl). For the room temperature Borax titrations the