Experiment 26 resluts only PDF

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Janesy Segui 11/22/19 Lab Partner: Bryan Amat Thermodynamics of the Dissolution of Borax Hypothesis The data will show the difference between endothermic and exothermic values. Report Data Table One. Standardized HCl Solution Trial 1 1. Tared mass of Na2CO3 (g)

Trial 2

Trial 3

0.155

0.151

0.151

0.00146

0.00142

0.00142

0

0

0

4. Buret reading, final (mL)

16.5

15.8

16

5. Volume of HCl added (mol)

16.5

15.8

16

0.00146

0.00142

0.00142

2.Moles of Na2CO3 (mol) 3. Buret reading, initial (mL)

6. Moles of HCl added (mol) 7. Molar concentration of HCl (mol/L)

8.84x10^-2

8. Average molar concentration of HCl (mol/L)

9.28x10^-2

9.56x10^-2

9.44x10^-2

Table Two. Preparation of Borax Solution Samples

Room Temperature Water

1. Volume of sample (mL)

5

2. Temperature of sample (degrees C)

Hot Water 25

Cold Water 40.5

5

3. Buret reading, initial (mL)

0

4. Buret reading, final (mL)

6.4

7.2

5.4

5. Volume of HCl added (mL)

6.4

7.2

5.4

6. Temperature, T (K)

298

313.5

278

7. 1/T (K^1)

3.36x10^-3

3.19x10^-3

3.60x10^-3

8. Moles of HCl used (mol)

1.45x10^-3

1.50x10^-3

5.66x10^-3

9. Moles of B4O5(OH)4^-2 (mol)

7.25x10^-4

7.50x10^-3

2.83x10^-3

10. [B4O5(OH)4^-2 (mol/L)

4.39x10^-2

4.75x10^-2

1.77x10^-2

11. Molar solubility of borax (mol/L)

4.39x10^-2

4.75x10^-2

1.77x10^-2

12.Solubility product, Ksp

9.10x10^-4

9.85x10^-4

3.67x10^-2

13. ln Ksp

-7

14. -Delta(H)IR 15. Delta(S)IR

-6.92

-7.91 -2505.5 1.2

16. Delta(H) (kJ/mol)

20.83

17. Delta(S) (J/mol*K)

0.01

18. Delta(G) (kJ), at 298 K

Calculations for Trail One: 1) 0.155/106= 0.00146 mol 2) Moles of Na2CO3=Moles of HCl 3) 0.00146/0.0165= 8.84x10^-2 (mol/L) 4) 8.84x10^-2+9.56x10^-2+9.44x10^-2 /3= 9.28x10^-2 (mol/L) 5) 25 degrees C + 273 degrees K=298 6) 1/298=3.36x10^-3 (k^1) 7) 0.0165*8.84x10^-3 (mol) 8) 1.45x10^-3(1B2O4(OH)5^-2/2 HCl= 7.25x10^-4 (mol) 9) 7.25x10^-4/0.0165= 4.39x10^-2 (mol/L)

-56.38

10) 0.144^2*4.39x10^-2= 9.10x10^-4 Ksp 11) ln(9.10x10^-4)= -7.00 Ksp 12) slope = -delta(H)/R 13) Delta (H)= 0.008314 kJ/mol*K * 2505.50 K = +20.83kJ/mol 14) Delta (S)/R = 1.20 15) Delta (S) = 0.008314 J/mol*K *1.20 = + 0.010 kJ/mol*K 16) Delta (G) = 20.83 kJ/mol – 298 K * 0.259 kJ/mol*K=-56.38 Discussion Experiment of Thermodynamics of the Dissolution of Borax, was performed to understand the objective of the lab exercise. Learning how to standardize a hydrochloric acid solution, and determine the solubility product of borax as a function of temperature. Last section will show the purpose is to determine the standard free energy, standard enthaply, and standard entropy changes for the dissolution of borax in an aqueous solution. The procedure was to start titrating the sodium carbonate with the HCl solution. Taking several different measurements shown in Tables One. The second procedure for the experiment was to then prepare different temperature water baths for the borax, shown recorded data in Table Two. While performing the experiment we then recorded all the important values that are needed to do the calculations. Finding the Ksp value, in order to calculate the titration of the borax solution using a measured concentration of HCl. Seven drops of Methyl orange to indicate the equivalence point of the borax and HCl solutions. It gave the value of the Ksp as, 9.10x10^4. In the graph of ln Ksp vs. 1/T shows the needed y-intercept form of the tread line in order to solve for the rest of the calculations. The trends were expected based on the background information in the lab manual.

Based on the theory the results were expected but due to error at any point the results can vary. Theories in the lab manual suggest that the higher temperature includes a higher Ksp. As well as when other calculations are higher and positive lead to the substance being endothermic and lower being exothermic. The results showed that my values were more exothermic because they were lower and negative. Errors that could have occurred were possible contaminated instruments and possible errors of any one who standardized the HCl solution. Conclusion To conclude with the thermodynamics of the Dissolution of Borax, the objectives were to learn about how to standardize a hydrochloric acid solution, and determine the solubility product of borax as a function of temperature. While also determining the standard free energy, standard enthaply, and standard entropy changes of borax. The procedure was to start titrating the sodium carbonate with the HCl solution. Then prepare different temperature water baths for the borax, to record all given and measured values. The results concluded that the Ksp and calculated data showed that it was exothermic reaction. Lab Report Questions 2) The endpoint in the titration is "overshot" a. Is the reported molar concentration of the hydrochloric acid solution too high or too low? Too low, because it has too much base. b. As a result of this poor titration technique, is the reported number of moles of B4O5(OH)4 2in each of the analyses too high or too low? Too high, because will still have more base. 3) The solid borax reagent is contaminated with a water-soluble substance that does not react with hydrochloric acid. As a result of this contamination, will Ksp of the borax be reported as too high, too low, or unaffected? Too high, because the molar solubility will be higher as well. 5) A "little more" than 5 mL of a saturated solution of borax is transferred to the corresponding calibrated test tube and subsequently titrated with the standardized hydrochloric acid solution. How will this "generosity" affect the reported molar solubility of borax for that sample...too high, too low or unaffected? It will be unaffected because the molar solubility will be high.

Reference Beran, J.A., Laboratory Manual for Principles of General Chemistry, Texas A&M University,10th edition: 2014, pp 305-314....