Titration 116

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Arizona State University *

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Feb 20, 2024

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Preparing a Standardized Sodium Hydroxide Solution Jazmin Perez, Gianni Johnson, Chiara Palacios, Maya Golic August 31st, 2023 Thursday /1:30 PM

Introduction The purpose of this experiment was to prepare a 0.1 M solution of NaOH, determine the actual concentration of the solution with the help of titration, and then store the prepared solution for later use in the semester. To be able to perform this experiment to obtain the most accurate results there were a total of four trials that were done. First, the 0.1 M NaOH solution was made using a volumetric flask and deionized water and after, for each trial, the amount of KHP was measured out. For the titration process, KHP was dissolved into an erlenmeyer flask with 20 mL of deionized water and two to three drops of the indicator was added to the erlenmeyer flask. Using the NaOH solution, titration was performed on the solution in the erlenmeyer flask. Lastly, the concentration of the NaOH was found using the data collected from the experiment. The learning goals for this experiment were to use our familiarity with acid-base titration as a method to obtain the concentration of the NaOH solution, with other learning objectives present, such as using stoichiometry and calculating molarity. With this information, additional learning goals were, calculating standard deviation and the accuracy of our concentration. Methods We were tasked with making a 0.10 M solution of NaOH from a 1 M solution of NaOH. We used titration as a means of finding the exact concentration of our solution meaning that we had to dilute the solution with Deionized water. Next, we took note of how many mL of NaOH were in our buret. We began with a constant controlled drip whilst one of us swirled the erlenmeyer flask. We decreased the interval over time in correspondence with how long the pink color lingered until we came to a solid light pink color. After this, we found the moles of KHP through the equation 0. 185g KHP X % = 9.059 x 10 ‘mols. Our answer needed to be in Liters

1L 1000mL — 0.00901L NaOH. We then used the so using stoichiometry we got 9. 01ml NaOH X 9.059x10 *mols KHP 9.01x10 L NaOH equation M =% (M = ) giving us 0. 1005M. Materials e DBuret e Buret stand e analytical balance e (.1M NaOH solution e KHP e Phenolphthalein e 125 mL Erlenmeyer Flask e Graduated Cylinder e Volumetric Flask e DI Water Procedure Begin the experiment by preparing a 0.1M NaOH solution. Measure 50 mL and pour it in a volumetric flask. Then, pour DI water into the volumetric flask up until the neck line. Then, pour your solution into the buret. Fill it up to 0 mL. Next, measure 0.15-0.30g of KHP by using the analytical balance. Record the weight for four trials. Then fill up 20 mL of DI water using a graduated cylinder, and pour that into the erlenmeyer flask. Next, add the KHP into the erlenmeyer flask with the DI water. Mix the solution until it is completely dissolved. After it is completely dissolved, add 2-3 drops of Phenolphthalein. After the solution has been created, you can start the titration. Make sure to record the initial volume for each trial as it will change

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throughout the experiment. Have one person hold the erlenmeyer flask under the buret and the other person add the NaOH. As the NaOH is being added, have the person holding the erlenmeyer flask swirl until a light pink color appears. When the solution changes color, titration can end and then the final volume on the buret can be recorded. After this you will repeat it for three more trials. You can then subtract the final volume minus the initial volume. From there, you will use this information to calculate the concentration of NaOH for each trial, find the mean from the four trials, and using this information you will calculate the standard deviation. Experimental Data Description Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Trial 6 Mass KHP Used (g) 0.2765 0.1850 0.2160 0.1824 N/A N/A Final Burette 13.68 22.69 10.10 22.38 N/A N/A Reading (mL) mL mL mL mL Initial Burette 0 mL 13.68 0 mL 10.10 N/A N/A Reading (mL) mL mL Volume NaOH Used 13.68 9.01 mL 10.10 12.28 N/A N/A (mL) mL mL mL Moles KHP Used 0.001354 | 9.059 x| 0.001058 | 8.931 X N/A N/A (mol) moles | 197* moles 10~* moles moles Concentration NaOH | 0.09897 | 0.1005 0.1048 0.07314 N/A N/A (mol/L) mol/L mol/L mol/L mol/L

Mean Concentration: 0.09435 mol/L Standard Deviation: 8.27 x 10—3 CalculationsCalculations 9.059x10 *mols KHP 9.01x10 L NaOH Sample calculation: M = 0.09897mol/L+0.1005mol/L+0.1048mol/L+0.07314mol/L _ . = 0.09435mol/L Mean calculation: Standard deviation: 2 2 2 2 0.09897-0.09435) +(0.1005—0.09435) +(0.1048—0.09435) +(0.07314—0.09435 -3 5 = )+ e )+ ¥ 827 x 10 827x10> % Confidence interval: 100 X (1 — —5=-) = 91.2% Discussion and Conclusion Based on the value you determined by titration for the sodium hydroxide concentration and the standard deviation, do your trials meet the desired precision (greater than 90% confidence)? How precise were your trials? Were there any obvious outliers? Based on the value determined by titration for the sodium hydroxide concentration and the standard deviation, our trials did meet the desired precision of 90% and above in confidence. Our trials were 9% off in precision, signifying the errors present. There were no obvious outliers present to disrupt our data. How accurate was your data (compared to the 0.100 M concentration we thought we were making)? What are possible causes of the discrepancy between the actual concentration of your sodium hydroxide solution and the goal concentration of 0.100M?

Our data compared to the 0.100 M was off but also somewhat close. With a calculated mean of 0.09435, it represents how for each trial we could've been more accurate in our measurements and readings of the measurements. What can you do to improve the precision if you were to do this experiment again? If we were to do this experiment again we could achieve better precision by running more trials with varying amounts of KHP within the given range. Another method of improving precision is standardizing the amount of drops of indicator used so that variation would be little. What can you do to improve the accuracy? To improve the accuracy we could achieve the ideal color on as many trials as possible. We could also make sure that all of the KHP makes it into the flask allowing us a more accurate reading. By making sure that a proper reading of the mL on the buret was being performed. We could also make sure that the titration process was going smoothly and was being controlled. Working one by one on specific trials all in our groups of two and setting different tactics/rolesis way to ensure accuracy as well. This way, we know that there will be little to no errors present when performing the experiment. Analysis (Post-Lab Questions) 1. Using your standardized sodium hydroxide solution, you titrate an unknown solution of acetic acid, C,HsO,, a monoprotic acid. What is the concentration of the acid if it takes exactly 20.00mL of your sodium hydroxide solution to neutralize 25.00mL

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0.0755mol/L . Using your standardized sodium hydroxide solution, you titrate an unknown solution of citric acid, C4H3O,, a triprotic acid. What is the concentration of the acid if it takes exactly 20.00mL of your sodium hydroxide solution to neutralize 11.25mL of citric acid? 0.1677mol/L Appendix P - A MUJ hH? \\!\0\&30‘? \/\'V‘M\ (o )mdné“f‘@a " g Com g Tyia) |/ 12). 8L D’@%c",'ﬂ:}w&w Yl 1o, Z“Tufius O_:——(-)_Pfi_erK.OUB i i —T;——O: w 0 -+ . L- O A gt TV\CX\?») O"K%Ugj 1.051AD fku} O_!_E-\-—wa""”' - TY \O\\ \Y\O\\ k) \%zb‘f) \% A%\ X |0 mo \’L.?/‘éml/ \ 0.0 1214 ‘f»‘,fi‘\/¥f/\/ EO T\ 0g lD Aombl {0043 SR s \O 1 00\Q®$ ywols e e ————— e — | 9