_Standardization of Sodium Hydroxide Lab Report - Emely Ramirez

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Standardization of Sodium Hydroxide Emely Ramirez CHEM 120B Laboratory, Spring 2023

Abstract The purpose of this experiment was to make a solution of 0.1 M Sodium Hydroxide that will eventually be standardized in order to determine the exact concentration of the prepared NaOH solution. The NaOH solution was titrated against Potassium Acid Phthalate with its known mass of the acid, in order to determine the NaOH solution concentration. It will also then eventually later be used as a reactant to make further measurements within the experiment. Phenolphthalein was used as an indicator to determine the equivalence point has reached the equal amount of moles within the base and the acid. It was found that the average NaOH concentration was 0.0919 M, the RSD % was about 1.58%, and the RE % was 15.7%. Introduction Standardization is the process of determining the exact concentration of a certain prepared solution using another primary standard solution. The purpose of this experiment is to determine the exact concentration of the prepared solution and to eventually later be used as a reactant to make further measurements within the experiment. 1 In this case the prepared 0.1M NaOH solution was titrated against an acidic salt known as Potassium Acid Phthalate (KHP). The chemical reaction is shown below. NaOH (aq) + KHC 8 H 4 O 4(aq) → KNaC 8 H 4 O 4 (aq) + H 2 O (l) (1) This equation just allows to simply obtain the actual volume of the NaOH solution that was titrated against the KHP acid solution. The Initial Volume Buret depends at where the NaOH solution was started at in the conditioned buret and the Final Volume of the Buret would be where it stops after the equivalence point has been reached. Volume of NaOH titrated = Final Volume Buret - Initial Volume Buret (2) The reason as to why KHP was used as an acid for the titration in this case was because it won’t absorb any water from the atmosphere that will allow a difference in mass when titrating, it’s highly soluble, non- toxic and has high purity. 2 The reason as to why we used titration in order to help determine the unknown molarity of the 0.1M NaOH solution would be because the known volume of the titrant that was added with the known mass of KHP will allow us to eventually determine the unknown concentration of NaOH solution. This equation will be used to determine a certain concentration of the NaOH solution within the trial. 2 Potassium hydrogen phthalate - labchem.com . LabChem - Safety Data Sheet . (n.d.). Retrieved February 21, 2023, from https://www.labchem.com/tools/msds/msds/LC18690.pdf 1 Standardization of Sodium Hydroxide. In CHEM 120B Laboratory Manual [Online] ;Matthew, B.Ed.; Macmillan Learning Curriculum Solutions: Plymouth, MI, 2020. Retrieved February 20, 2023, from class website at https://courses.com/mod/book/view.php?id=66663

(3) ? ???𝐻 = ? ?𝐻? ?? ?𝐻? 𝑉 ???𝐻 Essentially the molarity will be determined since it’s also known that the reaction has a 1:1 stoichiometry, meaning that the moles of the acid will be equal to the moles of the base. Which will then allow us to further determine the concentration of the NaOH solution more accurately and precisely. The indicator ( phenolphthalein) was used in order to help determine right before the prepared solution and acid reaches its equivalence point. The equivalence point would be known as the point where the moles of the acid are the same as the moles of the base. In other words the amount of volume added from the NaOH solution or the titrant neutralized the solution that contained the KHP acid and the indicator. The chemical reaction was determined when it started turning pink as enough of the NaOH solution was added to the KHP solution which eventually allowed us to determine the equivalence point that was reached right before it turns absolute pale pink or pink. The instruments that were used in order to help the process of standardization was a conditioned buret, and an Erlenmeyer flask to keep the known mass of the KHP with deionized water and 2-3 drops of the indicator (phenolphthalein). As well as a balance in order to help determine the known mass of the KHP acid that was used within each trial. Three trials will be conducted to determine the average concentration of the prepared 0.1M NaOH solution. The average NaOH concentration will be used to compare to the experimental NaOH concentration and further be used in order to calculate the RSD%, and RE %. The data from all trials and the number of trials will be used in order to help determine the average. (3) 𝐴?????? = ??𝑖?? 1+ ??𝑖?? 2 ... ??𝑖?? ? ?????? ?? ??𝑖??? (?) This equation will allow us to understand the relative standard deviation within a specific set of data around its mean. Determining whether the regular standard deviation is a small or larger quantity that would differ according to the difference within the data set all around the mean. The SD stands for the standard deviation, which is the average variability within the data set. Mean would be the average concentration that was calculated from the three trials of NaOH. RSD shows the precision of theNaOH solution concentration; an acceptable value would be less than 3%. (5) ??? % = ?? ???? 𝑥 100% The Relative Error percentage is used in order to calculate the absolute error compared to the actual measurements within the experiment. It helps to determine a better understanding of the experiment and its whereabouts within the data. It’s essentially a calculation that evaluates the accuracy within the calculations of the overall experiment.

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(6) ??% = |?ℎ?????𝑖??? − ?𝑥???𝑖??????| ?ℎ?????𝑖??? 𝑥 100% Experimental Day 1 Within the Standardization of the Sodium Hydroxide experiment, a solution was prepared that carried 0.1M of sodium hydroxide within a 500mL plastic storage bottle. There was a bit over 500 mL of Deionized water that was heated on a hot plate in order to remove any dissolved Carbon Dioxide from the solution. Once the Deionized water was cooled, it was ready to have been transferred into the the plastic storage bottle that was mixed with about 3.0mL of NaOH (base). Once the solution is made and shaken up, the actual standardization will start from the prepared solution. The prepared solution was labeled correctly with the accurate name and molarity (0.1M) of the solution. This prepared solution was then used in order for it to be standardized against the acidic salt. Day 2 The buret was conditioned before the start of having conducted any trials. The conditioned buret was used in order to titrate the prepared solution of NaOH against the KHP acid, until it eventually reached its equivalence point. Eventually having found the volume that was used up in order to calculate for overall unknown concentration of the NaOH prepared solution. The mass of KHP was obtained within each trial and recorded accurately. The Erlenmeyer flask was used in order to hold the KHP acid with the 2-3 drops of the indicator, and eventually the NaOH solution as it’s being titrated. 3 The initial and final volume of the buret was also recorded. In order to have avoided more sample loss, a small deionized water bottle was used to spray the weighing paper in order to try and obtain every accurate amount of the KHP mass that was recorded for that specific trial. The titration then started drop by drop, as the NaOH solution was transferred into the KHP solution, it carefully and eventually reached its equivalence point. Pink started to appear more often as the moles of the NaOH (base) started to reach up to the equivalent amount of moles within the KHP acid. The closer the equivalence point was reached, was when data was accurately recorded when it came to the volume that was actually being titrated into the solution. Once the equivalence point was past its point, the recorded volume of the last titration was used in order to find the concentration of the NaOH solution within that trial.The data was then calculated using the RSD%, the relative error % and the molarity equation in order to have the appropriate concentration of the solution. Results In each trial, the mass of KHP was measured out and the final volume was calculated specifically before the start of each trial. Each table is able to demonstrate the results from the 3 Standardization of Sodium Hydroxide. In CHEM 120B Laboratory Manual [Online] ;Matthew, B.Ed.; Macmillan Learning Curriculum Solutions: Plymouth, MI, 2020. Retrieved February 20, 2023, from class website at https://courses.com/mod/book/view.php?id=66663

trials and how that correlates behind the data that was obtained from the average concentration of NaOH, RSD %, the moles of KHP/NaOH and Standard Deviation. Table 1. The standardization results from the titrations of an acid (KHP) with its known mass and a prepared solution of NaOH. ______________________________________________________________________________ Trial 1 Trial 2 Trial 3 ______________________________________________________________________________ Mass of KHP Titrated (g) 0.4348 0.4612 0.4146 Initial Buret Volume (mL) 0 8.600 9.400 Final Buret Volume (mL) 23.55 24.20 22.10 Volume of NaOH Titrated (L) 0.02355 0.02420 0.02210 Moles of KHP 0.09041 0.09332 0.091862 Moles of NaOH 0.09041 0.09332 0.091862 The data from table one will be used in equation number #3 in order to find the corresponding molarity of the NaOH concentration for each specific trial. The final buret volume, the molar mass of KHP (204.22g), and the known mass of KHP was used in order to help determine the unique concentration of NaOHaccording to each trial. Once all three concentrations are calculated from the trials, the average and the standard deviation will also be calculated using the three concentrations as well. The Relative Standard Deviation % will also be calculated using the equation #5 with the input of SD and mean. The Relative Error % will be calculated using equation #6, with the inputs of the theoretical concentration and the experimental concentration. Table 2. The determined concentration of sodium hydroxide after three titrations with KHP along with the standard deviation and %RSD. ______________________________________________________________________________ Concentration of NaOH Average SD RSD % RE% ______________________________________________________________________________ Trial 1 0.09041 M 0.0919 M 0.001455 M 1.584 % 8.1% Trial 2 0.09332 M Trial 3 0.09186 M _________________________________________________________________________________________________________________________________

Discussion In this experiment our average concentration is able to tell how it was calculated from the three trials according to our specific recorded volumes titrated from the prepared NaOH solution. As well as the specific mass that was used for the KHP acid in order to eventually find the molarity of the NaOH solution for that trial. The RSD % is able to tell the actual standard deviation that occurred between all of the concentrations calculated within the three trials. In this case the RSD % was 1.58 % and anything lower than 3 percent will be considered that the data was successful enough. Overall the idea of being able to gain more of an understanding on how spread out the concentration was calculated within each trial. The relative error is there to help calculate any possible error that would be possible to fluctuate one’s own data from the actual data that should be calculated. Such errors like not reaching an appropriate volume before the equivalence point or losing a small amount of KHP before it was reached into the beaker. In this case our relative error % was 15.7% and anything bigger than a 5% would be considered a high measurement difference between the absolute error compared to the true value. However, in this case our RE% percent is bigger because it was focused more on the accuracy and similarity within each trail when it came to the concentrations for all three trials. It didn’t focus so much on the idea of any lost sample or any wrong weighing because its main goal was to present precision within all the trials for the concentration data. In this case the experiment was a success in the understanding of being able to reach a reasonable and appropriate unknown molarity from the prepared NaOH solution that consistently stayed within close proximity for each trial. Once the concentration is known, it will then be later used as a reactant to make further measurements in the experiment. Some possible errors that would explain the percentage of the relative error would be that there might have been some possible loss of the KHP when the transfer was being made into the Erlenmeyer flask. Therefore explaining a possible impact in our data interpretation and an explanation as to why there is more of a higher relative error % compared to my relative standard deviation %. Another could’ve been getting a wrong reading on the known mass of the KHP for each trial or even just miscalculating the final volume of the titrant by a few fractions of a mL. Conclusion The concentration of the prepared NaOH solution was successfully standardized and known as the experiment reached its final calculations to the average concentration of the three trials. Based on the RSD % from the three trials that were conducted it’s fair to say that an appropriate known concentration was reached from the NaOH solution. Some possible potential sources of error could have been lost sample and using a volume that passed the equivalence point when calculating for the NaOH concentration for the unique trial. Therefore explaining a possible reason behind the relative error and the smaller percentage within the RSD. The RSD formula allowed us to obtain the percentage of 1.58%, which allows us to understand that our average concentration for the solution was not too spread out within the data set of the three

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trials. Overall data was relatively consistent within all three trials that allowed us to complete our objective and have the solution standardized accordingly. References Standardization of Sodium Hydroxide. In CHEM 120B Laboratory Manual [Online] ;Matthew, B.Ed.; Macmillan Learning Curriculum Solutions: Plymouth, MI, 2020. Retrieved February 20, 2023, from class website at https://courses.com/mod/book/view.php?id=66663 Potassium hydrogen phthalate - labchem.com . LabChem - Safety Data Sheet . (n.d.). Retrieved February 21, 2023, from https://www.labchem.com/tools/msds/msds/LC18690.pdf SDS Search Page . Chemical Safety. (2023, February 10). Retrieved February 20, 2023, from https://chemicalsafety.com/sds-search/ Appendix Theoretical [NaOH] 2.85 mL (NaOH) * * * * = 0.1090 mol/L 1.53 ? (???𝐻) 1 ?? 1 ? (???𝐻) 2 ? ?????𝑖?? 1 ??? (???𝐻) 40 ? (???𝐻) 1 0.5 ? Target Grams of KHP 0.020 L (NaOH) * * * = 0.4452 g KHP 0.1090 ???/? 1 ? (???𝐻) 1 ??? (?𝐻?) 1 ??? (???𝐻) 204.22 ? (?𝐻?) 1 ??? (?𝐻?) Range of KHP Mass : 0.4452 g KHP * = 0.40068 g to 0.48972 g of KHP 10 100 Trial 1 [NaOH] = 0.09041 M (NaOH) ? ???𝐻 = 0.4348 ? * 1000 204.22 ? * 23.55 ?? Average [NaOH]- (Three Trials)

= 0.0919 M (NaOH) 0.09041+ 0.09332 + 0.09186 3 RSD % (Relative Standard Deviation Percentage) RSD% = * 100% = 1.58 % 0.001455 0.0919 RE % (Relative Error Percentage) RE % = |0.1090 - 0.0919| / (0.0919) * 100% = 15.7%