Chem 1008 Lab Report 5.docx - Name: Gladys Reyes-Palacios...

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Name: Gladys Reyes-PalaciosDate: March 22, 2018Section: 601TA Name: Pramathesh MajipH-TitrationsI pledge that the work submitted for this lab report is my original work and is inaccordance with the principles of academic integrity as defined in the statement onAcademic Dishonesty in the UNO Student Code of Conduct.Signature:GladysReyesDate: March 22, 2018
AbstractThis experiment was divided into two separate parts. For the first part of this experiment,NaOH was standardized using KHP. KHP was used as a primary standard for NaOHbecause an accurate concentration of NaOH cannot be prepared due to its high reactivitywith water. Therefore, KHP was used to indirectly determine the concentration of NaOH.Once the amount of NaOH used to neutralize KHP was determined, the concentration ofNaOH could then be found using stoichiometry since the amount of moles of KHP usedwas known as well. After three trial runs, the concentration of NaOH was found to be0.11 M. For the second part of this experiment we used the standardized NaOH todetermine the unknown concentration of a weak and strong acid. Triplicate titrations wereperformed for each unknown acid—the first trial was a test run. The concentration of HClwas found to be 0.14 M and the concentration of acetic acid was found to be 0.16 M.IntroductionThe purpose of this experiment was to follow the titrations of a strong and weak acid withsodium hydroxide, NaOH(aq). In order to do this, NaOH was first standardized and itsconcentration was determined.Acid-base titrations are a technique used in chemistry to determine the concentration ofan acidic or basic solution using a colored indicator or pH meter; in this lab both wereused. A useful indicator changes color quickly near its endpoint.1The goal of thesetitrations was to determine the equivalence point. If the proper indicator was selected,then the endpoint and the equivalence point would be very close to one another.2For thisexperiment phenolphthalein was used as the color indicator since it has a strong colorchange when it nears its pKa.3The pH meter was also used to record the pH of thesolution as the NaOH was added. Using this information the equivalence could also befound at the point where small additions of titrant caused a rapid rise in pH.In this experiment a strong acid, hydrochloric acid (HCl) and strong base, sodiumhydroxide (NaOH) were titrated and their neutralization reaction was:HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)(1)The titration was performed by adding standard NaOH to HCl of unknown concentration.The pH was recorded and the equivalence point was found. From the equivalence pointthe concentration of the unknown acid, HCl could then be found.The weak acid in this experiment was acetic acid. Weak acids, HA, can be titrated withNaOH using the same technique:HA(aq) + NaOH(aq) → NaA(aq) + H2O(l)(2)However, weak acids are different from strong acids when it comes to titrations in thatthey do not dissociate completely.4Due to this incomplete dissociation, the reaction is inequilibrium, with an acid dissociation constant, Ka, which is specific to that acid. The

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Term
Fall
Professor
Pheobe Zito

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