_Standardization of Sodium Hydroxide Lab Report - Emely Ramirez

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120B

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Chemistry

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Feb 20, 2024

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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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