Experiment 9 Formal Lab - Experiment 9 Determining Ksp and...

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Experiment 9 – Determining K sp and Thermodynamic Parameters Name: Emily Mou Chemistry 1A Partner: Niema R. GSI: Jennifer Yen August 1, 2007 Purpose : Observe the effect of temperature on the solubility product (K sp ) and thermodynamic parameters (ΔH° enthalpy, ΔS° entropy, ΔG° Gibb’s free energy) of a dissolution reaction. Methods : Saturated solutions of borax were prepared at various temperatures, and four samples at each temperature were taken and titrated to their endpoints with HCl (Table 1). The volumes of HCl were averaged and used to calculate the molarities of borax for each groups’ saturated solution, as the property of borax as a base meant the moles of HCl needed to titrate to endpoint were directly proportional to the amount of moles of borax in the solution. Class data was obtained and tabulated (Table 2) and the molarities of borax were used to attain the solubility products (K sp ) of the dissolution reaction. A Van’t Hoff plot (lnK vs. 1/T) (Graph 1) was made and an equation was generated using linear regression. In accordance with the Van’t Hoff equation, enthalpy (ΔH°) and entropy (ΔS°) were calculated from the slope and y-intercept of the linear equation, respectively, and subsequently Gibb’s free energy (ΔG°) was found for a specified temperature. Data : Table 1: Volume of HCl (0.5050 M) Used During Titrations of Borax Solution at 323.40K Trials 1 2 3 4 Average HCl (0.5060 M) (mL) 2.62 2.29 2.49 2.12 2.47 Table 2: Properties of Saturated Borax Solutions at Various Temperatures Group Temp. (K) Volume (L) HCl (*10 -3 ) moles of H 3 O + (*10 -4 OH - moles of B 4 5 (OH) -2 sample size (L) M B (moles/L) K (*10 1/T (1/K o lnK 1 274.25 2.04 10.32 10.32 5.16 .005 10.32 0.44 3.65 -5.43 2 275.00 1.70 8.60 8.60 4.30 .005 8.60 0.26 3.64 -5.97 3 277.00 1.80 9.11
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This lab report was uploaded on 04/06/2008 for the course CHEM 1A taught by Professor Nitsche during the Summer '08 term at University of California, Berkeley.

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Experiment 9 Formal Lab - Experiment 9 Determining Ksp and...

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