AcidBase Titrations Standardized Solutions Report.docx -...

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Chemistry Lab 114 – R5Acid and Base Titrations: Preparing Standardized SolutionsPurposeThe purpose of this experiment is to perform two titrations to prepare a standardized solution ofsodium hydroxide (NaOH) and a standardized solution of hydrochloric acid (HCl). Thestandardization of a solution provides the exact concentration of the solution to four significantfigures, which will be needed in the experiment for next week. Theory The theory behind this experiment is to apply the principles of a titration with an indicator todetermine the equivalence point of the titration, which is then used to calculate the concentrationof the standardized NaOH solution and the concentration of the standardized HCl solution. Thetitrations performed in this experiment are part of a process known as standardization, which isdefined as the method of determining the exact concentration of a solution. Standardization canbe accomplished by using a primary standard, a reagent that is easily weighed and of such a highpurity that its weight is representative of the exact number of moles of substance contained in thesample. In addition to being of high purity, the primary standard must also be of knowncomposition and it must react with known stoichiometry. This is because contaminants cannotinterfere with the titration reaction (or the equivalence point will be off from the true value) andthe calculations of the concentrations for the two standardized solutions can only be performed ifthe chemical formula and the stoichiometry of the reaction are known. There are alsorequirements for the titration reaction: the reaction must be fast and of exact and knownstoichiometry and it must have a method of detecting the end point. In this experiment, anindicator will be used to detect the end point of the titration. A chemical indicator is a substanceor dye that changes color at a specific pH value. The indicator used in this experiment isphenolphthalein (C20H14O4), which turns a characteristic pink color in solution when theequivalence point of the titration has been reached. In the standardization of the NaOH solution,the primary standard compound used is potassium hydrogen phthalate, also known as KHP(KHC8H4O4). KHP reacts in a 1:1 ratio with sodium hydroxide, so the number of moles of KHPused is equal to the moles of NaOH in the standardized solution titrant, which is then used tocalculate the molarity of the NaOH solution based off of the volume of NaOH used to titrate theKHP sample. In the standardization of the HCl solution, the primary standard used is thestandardized NaOH solution. Similarly, the NaOH solution reacts in a 1:1 ratio with hydrochloricacid, so the number of moles of NaOH used is equal to the moles of HCl in the HCl solutionsample, which is then used to calculate the molarity of the HCl solution based off of the volumeof HCl in the titrated sample.

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Term
Fall
Professor
N/A
Tags
Chemistry, HCl Solution

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