Please refer to notebook c claims for the reaction

This preview shows page 2 - 3 out of 3 pages.

Please Refer to Notebook Pages 34 - 35 C. Claims For the reaction that occurs when borax is dissolved in water ΔH° equaled 94.2 kJ/mol, ΔS° equaled 2.5 x 10 2 kJ/(mol∙K) and ΔG° equaled 9.27 kJ/mol. The reaction was endothermic and non-spontaneous. D. Evidence The thermodynamics of the reaction that occurs with borax and water can be determined graphically by the linear relationship of enthalpy change, entropy change, free energy change and the solubility constant. To determine this linear relationship, the solubility constant was first determined using the concentration of sodium and tetraborate ions. For our first trial, the solubility constant was found to be .0916 and increased with increasing temperature. Using these values with the inverse values of temperature, we were able to determine the linear equation. Relating the slope to enthalpy, ΔH° was calculated to be 94.2 kJ/mol, and using the y-intercept, ΔS° was calculated to be 285 kJ/(mol*k). From these values, the free energy change could be determined at room temperature, and was calculated as 9.7 kJ/mol. Since the change in enthalpy was found to be positive, the reaction could then be deduced to be endothermic. This is reasonable since the molar solubility increased with increasing temperature, suggesting that more borax was able to dissolve when energy was put into the system. Furthermore, the reaction could be determined to be non-spontaneous once the free energy change was found to be positive.
E. Reflection a. The solvation of Borax in water is and endothermic reaction. b. The solubility of borax increases as temperature increases. c. If some solid borax had been transferred along with the saturated solution, the mL of HCl needed to titrate the solution would have increased. This would have affected the apparent moles of Borax and shifted the plot slightly upward, towards a more positive slope.

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture