Mesa Community College CHM MISC ThermoLab 9201 Lab Questions

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Maddie Cunningham Toto Chem 201 L May 2020 Thermo Lab Questions 1. What do we expect for the magnitude of Ksp (e.g. > or < 1) since this is a soluble salt? 2. Do you expect the dissolving of K... NO 3 to be endo or exothermic and why? 3. Do you expect the entropy to increase or decrease when a salt dissolves in water and why? 4. Based upon what you know of nitrate salts, will KNO 3 dissolve spontaneously? (explain) 5. Using the Literature Reference Values for the H 0 f , G 0 f , and absolute entropy, S 0 , given in the below table, find the theoretical values of ∆H Rxn o , ∆Srxn o , and ∆Grxn o for the dissolving of KNO3(s). Cunningham 2 6. Use the mass of the KNO3 to calculate the number of moles of KNO3 present. Find in Table 1. 7. Determine the total amount of water delivered (mL) for each trial. Find in Table 2. 8. Determine the Tequil average (oC) from the three T values given. Find in Table 2. 9. Fill in the average temps from Table 2 into Table 3. 10. Into Table 3, calculate the molar concentration of KNO3 (M) in the solution at each temperature using the number of moles of KNO3 (from Table 1) and the volumes ``amount delivered” (Table 2) at each temperature. Because nearly all the KNO3 is still dissolved in solution, the molar concentrations of K+ and of NO3 - are equal to the moles of KNO3 initially present divided by the total volume of solution in L. 11. Use equation 5 from the lab manual: K sp = [K+] [NO3 - ] to calculate the temperature dependent solubility. 12. Use the total amount of water delivered to estimate the solubility in units of gKNO3/100gH2O. Assume that the density of water is 1.00 g/ml. 13. Using Excel, graph solubility of KNO3 as a function of temperature. [This is a topic from Chemistry 200. See Chapter 11.3]. product constants, Ksp, for dissolving KNO3. 14. Compare the plot to the literature (your text book or google solubility of KNO3 versus temperature) and make sure you reference the source in your report (for example, see page “xxx” in [Show More]

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