Lab 7 - Lab 7 Determination of composition of impure weak...

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Lab 7:Determination of composition of impure weak acidThanuka UdumullaLab Partner –Wei Ming WangAnalytical Chemistry Lab – Chem 323-03Experiment performed – 11/05/201511/12/2015
Udumulla |2AbstractThe experiment was carried out to determine the composition of an impure KHP (WA3) sample using the method of titrimetric. NaOH solution was standardized with a known pure solution of KHP and used to titrate a solution made using a KHP (WA3) sample of unknown purity. The average molarity of the standardized NaOH solution was 0.1167 M ±0.0001, and the standard deviation and relative standard deviation of the standardization titrations were 0.000332 and 0.28%, thus indicating a high precision. The average purity of the impure KHP sample was 81.6% ±0.1 and the standard deviation was 0.046332. The statistical data shows that the results of the experiment are precise and they are valid.IntroductionIn this experiment the Composition of impure weak (WA3) acid is determined through titration with a strong base. The samples are prepared with using a known weak acid of unknownpurity and titrated to find out the true content of the weak acid in the samples. The method of measuring the volume of a reactant that is required to react with an analyte is called volumetric analysis and titration is a form of volumetric analysis (1). In this experiment acid-base titration is used to determine the amount of weak acid in the sample. In acid-base titrations, a standardized base (titrant) is added quantitatively to a solution with a particular acid with unknown concentration till completion of the reaction occurs. At the completion of the reaction, the titrant used can be measured and this can help to determine the amount of the unknown acid that was in the solution. Usually an indicator is used to signal the completion of the reaction (end point), but the most accurate acid-base titrations are carried out using pH meters that indicates the pH at the complete neutralization.Fig. 1- Acid-base titration setup (2)Fig. 1 shows the basic setup for an acid-base titration. The burette contains the standardized base and the beaker contains the unknown acid. The electrode of the pH meter is placed inside the
Udumulla |3beaker to measure the pH change that is occurring. A magnetic stirrer is place inside to ensure good mixing of the reactants.Similar technique is used to standardize the NaOH which is a used in this experiment. Due to the reactivity of the NaOH with atmospheric CO2it should be standardized. Using primary standard KHP of known quantity the concentration of NaOH can be determined and standardized. This standardized NaOH can be used to perform titrations. This experiment is a titration between the impure weak acid (WA3) Potassium HydrogenPhthalate (PHT) and the standardized strong base Sodium Hydroxide. Sodium hydroxide strong base is introduced in to the titrating beaker with weak acid Potassium Hydrogen phthalate and this results in a complete reaction between the two reactants.

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