Experiment 17 Lab report PDF

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Lab report over experiment 17, Household Chemicals
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Ryan Lammert CHE 113-021 Zhoudong Chai Somya Maratha December 2, 2021

Measuring Calcium Hydroxide’s Solubility Introduction: The purpose of this lab was to perform a trio of trials for each of two unique titrations, to be able to calculate the solubility product (ksp) for Calcium Hydroxide. To obtain the information from these titrations one must calculate the hydroxide concentration in a standard solution of calcium hydroxide, (French et, al. 98). Solubility has various factor that are necessary to account for such as, pressure, temperature, and the solute used. To start the experiment a standard solution of calcium hydroxide must be made. The key to this part of the experiment is obtaining the maximum amount of dissolved solution, therefore a filtration process will be used as well once the initial standard solution is obtained. For the titrations, the dissolution of the solute (Ca(OH) 2) is also a key factor in determining the required volume of the titrant used and also when analyzing the equivalence point. The final observation that one is looking for at the end of the titration is that the maximum amount of the solute must be dissolved, (French et, al. 98).

The initial titration is done to create a standard saturated solution using sodium carbonate, and hydrochloric acid so that the concentration of HCl may be determined. This is referred to as creating a primary standard which will then be standardized by Ca(OH)2 to determine the final solubility product of Ca(OH)2, (French et, al 98). The chemical reaction referred to can be shown by the following molecular equation: Na2CO3 + 2 HCl → CO2 + H2O + 2NaCl (French et, al 98). This titration will lead to the ability to calculate the molarity of HCl which is a fundamental part in calculating the ksp for Ca(OH)2. There are also two expected equivalence points to be measured for this primary titration as well. The second and final titration is the titration of the standard Ca(OH)2 solution using HCl as the titrant once again. The solubility product will be much easier to obtain now that the concentration of HCl has been calculated. Therefore, once the titration is complete, all the key factors, the concentration of HCl, the volume of the titrant used, and the volume at the equivalence point. This titration contradicts the initial one as it only is expected to obtain one equivalence point. (French et, al. 98-99). The reaction can be shown by the following equation: 2 HCl + Ca(OH)2 → CaCl2 + 2 H2O (French et, al 98). Methods: Materials: -

Na2CO3

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HCl solution

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Ca(OH)2

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Storage bottles

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pH sensor

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drop counter

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MeasureNet

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Glassware (French et, al 99).

Procedure: 1. Prepare Ca(OH)2 solution -

Obtain beaker of water

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Fill beaker with Ca(OH)2 until fully dissolved, add more until it doesn’t dissolve

2. -

Obtain 0.200g of Na2CO3, take three samples record the mass

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Create three Na2CO3 solutions with 20 mL of DI water in a 100 mL beaker, stir until dissolved.

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Obtain buffers with 4 pH and 10 pH, just enough to cover the tip of the probe

3. Set up MeasureNet -

Main menu → pH. mV → pH vs. volume → Calibrate → enter temperature → calibrate with 4 pH buffer → rinse then calibrate with pH 10 buffer

4. Add 0.2 M HCl to burette and record initial volume. 5. Start titration, watch for equivalence points and stir in Na2CO3 for smooth curve. 6. Stop MeasureNet, record final volume, enter into the MeasureNet, save as 001

7. Repeat steps 4-6 with other 2 solutions, save as 002, and 003. 8. Filter Ca(OH)2 solution by wetting filter paper with DI water over a 125 mL flask 9. Calibrate MeasureNet using the same method as step 3 10. Put 25 mL of Ca(OH)2 solution into 100 mL beaker 11. Fill burette with 0.2 M HCl 12. Titrate Ca(OH)2 whilst also swirling, save as 004 13. Repeat steps 10-12 for two more trials, save as 005, and 006. 14. Clean up lab table, and materials and put away nicely. Discussion: The purpose of this lab was to calculate the solubility product for calcium hydroxide after obtaining key factors from two titrations. The solubility product was calculated to be 2.75 E -5 for calcium hydroxide. From this the percent error was calculated using the accepted value of calcium hydroxide of 6.5 E -6 (“Webassign.net”). The percent error obtained from those two numbers was found to be 295% which shows that our value obtained was not accurate. A potential source of error may have resonated from the titration process. It isn’t impossible however it is difficult to be able to see the exact time when the first drop is titrated and when or if its recorded. Along with timing the end of the titration and stopping the MeasureNet. Therefore, the amount of HCl that may have been recorded may have been more than what was recorded. Nevertheless, the calculation which requires the amount of HCl used was calculated correctly, however the recorded values used for the calculation may have been wrong.

Another potential source of error could have come from measurements themselves whenever measuring mass of the solute and the volumes of the liquids. This is the least likely potential source of error as the measurements were done with the proper materials however human error is always something that one may account for. Although I believe that our measurements were correct and done correctly, it is not a possibility that can be eliminated. Therefore, if any of the measurements were wrong or measured and the values recorded were not the actual values, then that could have also affected the result. The third and final potential source of error is also the most likely error that could have occurred. Whenever creating the standard solution for calcium hydroxide, we dissolved all the Ca(OH)2 as required, however we may not have added enough to see the maximum amount dissolved. Our solution came out to be more slightly more translucent than some of the other groups who may have done the process of creating the standard solution correctly. In addition to that, out filtration process did not leave behind much of the solution indicating it may have been able dissolve more of the solute. This is the most likely due to the solubility product to being calculated much lower than the accepted value, along with the visibility through the solution created. Conclusion: This lab has taught me a many of techniques and observations to stay keen on. I have learned how the creating of a primary standard and a standard solution can be used to calculate the solubility product of a compound. In addition to that I learned about how the filtration and standardization of a chemical is important. Being able to see the maximum amount solvent can take of the solute is essential for the accuracy of the titrations. Learning how to calculate the solubility and having the knowledge is important for things in our

everyday life such as purifying water, making coffee, and things such as soap or shampoo. Although the result of the lab deviated greatly from the accepted amount for calcium hydroxide, I learned mostly about the carefulness and attentiveness necessary for the creation of a standard solution. Being able to determine the maximum amount a solute can be dissolved in a solvent is essential for the health and safety of everyone in the world.

Work Cited: French, April N., Allison Soult, Stephen Testa, Meral Savas, Francois Botha, Carolyn Brock, Charles Griffith, Darla Hood, Robert Kiser, Penny O’Conner, William Plucknett, Donald Sands, Diane Vance, William Wagner. “Using MeasureNet and Probes.” Chem 113 General Chemistry II Lab Manual. Plymouth, M: HaydenMcneil, 2018. 37-50. Web. 2 December 2021. https://www3.chem21labs.com/labfiles/36194_48_1-4_FrenchA%202187-1%20W20..pdf? rf=6784

French, April N., Allison Soult, Stephen Testa, Meral Savas, Francois Botha, Carolyn Brock, Charles Griffith, Darla Hood, Robert Kiser, Penny O’Conner, William Plucknett, Donald Sands, Diane Vance, William Wagner. “Solubility of Calcium Hydroxide” Chem 113 General Chemistry II Lab Manual. Plymouth, M: Hayden-Mcneil, 2018. 97-100. Web. 2 December 2021. https://www3.chem21labs.com/labfiles/36194_48_Exp%2017_FrenchA%2021871%20W20..pdf?rf=2023

Solubility Product for Calcium Hydroxide - Webassign.net Web. 2 December 2021. https://www.webassign.net/labsgraceperiod/ucscgencheml1/lab_10/manual.pdf...