97%(33)32 out of 33 people found this document helpful
This preview shows page 3 - 4 out of 4 pages.
in linear form y = mx+b, and the determination of K of the reaction at each temperature. The values can be used to form a linear equation where ln Ksp= y and x = 1/T. The determinations of ln Kspand 1/T were calculated when performing the titration with HCl at different temperatures and the van Hoff plot with ln Ksp = y and 1/T = x as described above refer to figure 1. Using the graph the values of the unknown can then be solved for, the slope of the line is used to determine the change in enthalpy and the y-intercept is the change in entropy, refer to figure 1. The experimental values of ∆H and ∆S are -1376.5J and 3.83J/k respectively, refer to figure 1 and calculations. These determinations are not very accurate because some of the groups titration values were not within 1% making the measurements not very precise with the van Hoff plot having a R2value of 0.3018, this number is nowhere close to one, refer to figure 1 and table 1 and table 2.
By using, a fully saturated solution of aqueous borax and titrating with 0.2500M HCl and using bromocresol green as the indicator the point in which the tetraborate ion was fully titrated. The titration was performed at six different temperatures to find different equilibrium constants at each temperature, plotting these points on a graph then finding the linear trend-line ofy = -11444x + 31.8. this gives the values for ∆H° and ∆S°, because -11444 = ∆H°/R and 31.8= ∆S°/R refer to figure 1.The borax reaction has to be endothermic because the solubility increases as the temperature increases forcing the reaction to shift increasingly to the right as the temperature increases. The higher the temperature, the more borax will dissolve in the water. The Kspat 22°C was 0.0016 M3. The Kspfor 25°C was 0.0045M3, the Ksp for 30°C was 0.0025 M3, the Kspfor 35°C 0.0021M3, the Kspfor 40°C 0.076M3, and the Kspfor 45°C was 0.074M3 , refer to table one and two. Even though the data from the experiment is not very precise, the values were still going up with higher temperature.