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Saturated Solution of Thermodynamics and Equilibrium Lab Report

Saturated Solution of Thermodynamics and Equilibrium Lab Report

Daniel Kevins

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Group Member Names:

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Question #1. In your own words, describe the goal(s) of this experiment.

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Calculation #1. Saturated solution sample temperature data

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Enter the temperature data you recorded for your saturated Borax samples.

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Calculate the mean temperature in units of C and K, and then calculate 1/T (1/K).

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Report Table 1. Temperature data and calculation results.

sample	initial temperature (before sampling), ^oC	temperature after sampling (^oC)	mean temp (^oC)	mean temp (K)	1/T (1/K)
45A	45.0	44.5
45B	44.5	43.9
35A	35.2	35.0
35B	35.0	34.5
25A	25.8	25.7
25B	25.7	25.7
15A	15.7	15.6
15B	15.6	13.2
5A	5.6	5.6
5B	5.6	5.3

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Question #2. (0.5 pt.) Record the concentration of the standard solution of HCl.

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0.1962

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Calculation #2.

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Enter the volume of HCl solution required to reach the endpoint in each of your titrations.
Calculate the molar equilibrium concentration of B₄O₅(OH)₄^2‒ in each borax sample solution your group titrated. (Refer to equation (7) in the lab for the molar ratio.)
Calculate a value of K_sp and ln K_sp for each sample solution. (Refer to equation (6) in the lab).

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Report Table 2 Equilibrium Concentrations of B₄O₅(OH)^2‒ from Titrations of Saturated Solutions of Borax at Different Temperatures, and K_sp and ln K_sp values.

sample	volume of HCl required to reach endpoint (mL)	equilibrium concentration of B₄O₅(OH)₄^2‒(M)	K_sp	ln K_sp
45A	21.9
45B	23.5
35A	46.6-21.9=24.7
35B	47.9-23.5=24.4
25A	15.2
25B	14.1
15A	27.6-15.2=22.4
15B	26.0-14.1=11.9
5A	33.2-27.6=5.6
5B	33.5-26.0=7.5

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Calculation #3. Show an example calculation for the equilibrium molar concentration of B₄O₅(OH)₄^2‒ using the titration data for sample 35A.

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►Include units and show all work, including the molar ratio of acid to base.

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Calculation #4. Show an example calculation for the value of K_sp using the data for sample 35A. Refer to equation (6) in the lab.

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►Use appropriate significant figures and show all work.

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Question #3. Using Excel 365, construct a graph by plotting ln K_sp(y-axis) versus 1/T (x-axis) using data from the 10 samples of saturated borax solution. Make sure to use the mean temperature in units of K. Create a best-fit line (trendline) through the ten data points and determine slope and y-intercept of the line. Insert an image of your ln K_sp versus 1/T graph below.

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►Label the axes, provide a title, and display the best-fit line (trendline) and equation on the graph.

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Calculation #5. Calculate the values of ΔH^o (in kJ/mol) and ΔS^o(in J/molK) using your experimentally determined slope and y-intercept values from your graph of ln K_sp vs. 1/T. Refer to equations (10), (11), and (12) in the lab.

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►Include proper units (see above), use appropriate significant figures, and show all work.

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Calculation #6. Calculate the value of ΔG^ousing equation (8) (ΔG^o = −RT ln K_sp) and the data for sample 35A. Enter your result in Report Table 3 below (Calculation #8).

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► Use appropriate significant figures and show all work.

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Calculation #7. Calculate the value of ΔG^ousing equation (9) (ΔG^o = ΔH^o – TΔS^o) and the data for sample 35A. Enter your result in Report Table 3 below (Calculation #8).

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►Use appropriate significant figures and show all work.

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Calculation #8. Calculate the value of ΔG^o (in kJ/mol) by using equation (8) (ΔG^o = −RT ln K_sp) and by using equation (9) (ΔG^o = ΔH^o – TΔS^o) for the nine remaining samples of saturated borax solution.

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Report Table 3. Calculated Values of ΔG^o using Equation (8) and ΔG^o using Equation (9)

sample	ΔG^o (kJ/mol) using ΔG^o = −RT ln K_sp	ΔG^o (kJ/mol) using ΔG^o = ΔH^o – TΔS^o
45A
45B
35A
35B
25A
25B
15A
15B
5A
5B

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Question #4. Does the value of the equilibrium constant change as the temperature changes? If so, explain why the value changes.

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Question #5. Compare your experimentally determined value for K_sp at 25^oC (i.e. samples 25A and 25B) with the accepted value of 1.8 x 10^‒2. Are they the same? If they are not the same, explain how they differ. How might you modify the design of the experiment to improve the experimental results (i.e., to produce values that are in better agreement with the theoretical values)?

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Question #6. Consider your experimentally determined value of ΔH^o for the dissolution of borax in water. Is this process exothermic or endothermic? Explain using your data and results.

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Question #7. Based on your observations in this experiment, predict the sign of ΔS^o for the dissolution of borax in water. What is the sign of your experimentally determined value for ΔS^o? Are they consistent? Why or why not?

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Question #8. Based on your experimentally determined value for ΔG^o at 25^oC, is the dissolution of borax in water a spontaneous process? If not, why does borax dissolve in water? Explain. (Hint: think about the difference between ΔG^o and ΔG.)

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