CHEM 152 Lab 1 Report
CHEM 152 Lab 1 Report CHEM 152
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This 5 page Class Notes was uploaded by Angel Lee on Tuesday June 9, 2015. The Class Notes belongs to CHEM 152 at University of Washington taught by Kevin O'Malley in Spring 2015. Since its upload, it has received 1103 views. For similar materials see General Chemistry in Chemistry at University of Washington.
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Date Created: 06/09/15
Name Section ID Number Lab Partner Chem 152 Experiment 1 Weak Acid Titrations By signing below you certify that you have not falsified data that you have not plagiarized any part of this lab report an d N t that all calculations and responses other than the reporting of raw data are your own independent work Failure to sign 0 e39 this declaration will result in 5 points being deducted from your report score All sections Of this report must Signature be typed Total Points 60 pts 5 pts notebook 55 pts template Notebook Pages Your notebook pages will be graded for general organization and completeness Can your TA easily find and read the data heshe is looking for PURPOSE AND METHOD Clearly state the purpose of this lab Explain how this is accomplished in this experiment What calculations do you need to perform What measurements will be made Do not provide experimental details here How do you go from calculatedmeasured values to accomplishing stated purpose 4 pts The purpose of this experiment is to determine the concentration of weak acetic acid This will be accoplished in the experiment by titrating the acid solution with the strong base sodium hydroxide utilizing phenolphthalein to indicate the equivalence point In the first part of the experiment NaOH will be standardized using KH P a weak acid to determine the molarity of NaOH up to three decimal points Because the reaction between KHP and NaOH is 1 to 1 moles of KHP moles of NaOH at the equivalence point Therefore since we can determine the moles of NaOH and the volume of NaOH added by subtracting the initial buret reading fro m the final buret reading the molarity of NaOH can be determined through the equation NaOH moles of KHP liters of NaOH After the concentration of sodium hydroxide is known sodium hydroxide will be used to titrate an unknown solution of acetic acid until the acid base indicator phenolphthalein changes the solution color into a faint pink at the equivalence point Because the reaction between acetic acid and NaOH is 1 to 1 moles of acetic acid moles of NaOH at the equivalence point Therefore we can use the calculated molarity from the first part of the experiment to attain the number of moles acetic acid through the equation NaOH liters of NaOH titrated moles of NaOH moles of acetic acid This enables us to calculate the final molarity of acetic acid through the equation acetic acid moles of acetic acid liters of acetic acid where the liters of acetic acid is given and estimated to be 0020 liters through an automatic dispenser I Standardization of NaOH using KHP Run 1 Run 2 Run 3 Mass of KHP 0301 9 Mass of KHP 0304 9 Mass of KHP 0303 g Molar Mass KHP 20422 gmole Molar Mass KHP 20422 gmole Molar Mass KHP 20422 gmole Moles KHP 000147 mol Moles KHP 0001489 mol Moles KHP 000148 mol Initial buret reading 160 mL Initial buret reading 1635 mL Initial buret reading 3119 mL Final buret reading 1632 mL Final buret reading 3119 mL Final buret reading 4609 mL mL Titrated 1472 mL mL Titrated 1484 mL mL Titrated 1490 mL L Titrated 001472 L L Titrated 001484 L L Titrated 001490 L NaOH 0100 M NaOH 0100 M NaOH 0100 M Average NaOH 0100 M Standard Deviation 00004 Sample calculation of NaOH from the standardization titration Use the data from Run 1 6 pts NaOH moles of NaOH moles of NaOH at equivalence point moles of KHP at equivalence point liters of NaOH NaOH moles of KHP 0301 g KHP 20422 qmol KHP 000147 mol KHP 0100 M NaOH liters of NaOH 1632 mL 160 mL1 L 1000 mL 001472 L NaOH ll AcidBase Titration CH3COOHNaOH Run 1 Run 2 Run 3 Initial buret reading 015 mL Initial buret reading 2016 mL Initial buret reading 1865 mL Final buret reading 2016 mL Final buret reading 411 mL Final buret reading 389 mL mL NaOH Titrated 2001 mL mL NaOH Titrated 2094 mL mL NaOH Titrated 2025 mL L NaOH Titrated 002001 L L NaOH Titrated 002094 L L NaOH Titrated 002025 L Moles NaOH 000200 moles Moles NaOH 0002094 moles Moles NaOH 000203 moles mL of acetic acid 20 mL mL of acetic acid 20 mL mL of acetic acid 20 mL L of acetic acid 0020 L L of acetic acid 0020 L L of acetic acid 0020 L acetic acid 010 M acetic acid 010 M acetic acid 010 M Average acetic acid 010 M Standard Deviation 00024 Sample calculation of acetic acid from the titration with NaOH Use the data from Run 1 6 pts Acetic acid moles of acetic acid moles of acetic acid moles of NaOH at equivalence point liters of acetic acid Acetic acid moles of NaOH M NaOHL of NaOH 0100 M NaOH002001 L NaOH 000200 mol NaOH 010 M acetic acid Calculate the expected pH of the solution at the equivalence point using YOUR AVERAGE VALUES for the concentrations of NaOH and acetic acid and the volumes of each that you used Just like in Prelab Q3 you will only have the conjugate base and spectator ions present at the equivalence point in a volume that is the sum of the volumes of acid and base you combined The Ka for acetic acid is 18 X 105 6 pts acetic acid hydroxide ion gt acetate water acetate water gt acetic acid hydroxide ion l 10 M 10 M 0 l 10 M 0 0 C 10 M 10 M 10 M C X X X E 0 0 10 M E 10 x x x Kb 56 1010 acetic acid OHquot acetate 1 0x x 24 10395 pOH 462 pH 938 Questions 1 If you use 30 mL of H20 to dissolve the KHP instead of 20 mL what is the expected effect on the calculated NaOH concentration Will the calculated concentration of NaOH be higher or lower than it should be Explain your reasoning 5 pts If I used 30 mL of water instead of 20 mL to dissolve the KHP there should have been no effect on the calculated NaOH concentration because the number of moles does not change Since the number of moles of KHP does not change the number of moles of NaOH does not change also In addition because the amount of liters is the positive difference between the buret readings adding more volume to the beaker does not have any effect on the values that were used to calculated the NaOH concentration Therefore the calculated concentration of NaOH does not change 2 If you overshoot the endpoint of the KHPNaOH titration what is expected effect on the calculated concentration of the NaOHaq Will the calculated concentration of NaOH be higher or lower than it should be Explain your reasoning 5pts If I had overshot the endpoint of the KHPNaOH titration there would have been an excess of volume of NaOH Although the number of calculate moles of NaOH does not change because it relies on the measured mass of KHP this excess volume of NaOH would effect the calculated concentration by increasing the measured liters of titrated NaOH Since concentration is calculated by dividing the number of moles by volume an increase in the volume of titrated NaOH would produce a calculated concentration of NaOH lower than it should be 3 If you overshoot the endpoint of the acetic acidNaOH titration what is the expected effect on the calculated concentration of acetic acid Will the calculated concentration of acetic acid be higher or lower than it should be Explain your reasoning 5 pts If I had overshot the endpoint of the acetic acidNaOH titration the volume of NaOH titrated would have increased thereby increasing the calculated moles of NaOH because this is calculated by multiplying the volume by the calculated concentration of NaOH in part 1 As a result this increase in calculated moles of NaOH would have increased the calculated moles of acetic acid because it is assumed the moles of NaOH and acetic acid are equal at the equivalence point On the other hand the give volume of acetic acid would have remained constant In conclusion because the concentration of acetic acid is calculated by dividng the moles of acetic acid by the volume an increase in moles would produce a calculated concentration of acetic acid higher than it should be 4 In the titration of acetic acid 20 mL of the acid are titrated with NaOH If 25 mL of acetic acid was used instead will this affect the determination of the acetic acid concentration and if so how Explain your reasoning 5 pts In a perfect world without quotnoisequot the calculated concentration of acetic acid should not be different with an increase in the volume of acetic acid used because as the number of moles of acetic acid increases the amount of volume required to titrate the solution IVVIuIIIIV VI MUVL V uVIVI VIVVVI MVUMUUV VLV II IV IIuIIIIIVVI VI IIIVIVV VI MUVLU uVIVI II IVI JMUVU I IV uIIIVuII II VI VVIuIIIIV IVVIUIIIVVI IV III LU I IV VVIuI IVII Laboratory Waste Evaluation 1 pt Laboratory waste is considered anything generated during an experiment that is disposed of down the sewer drain thrown in the garbage collected in a container for disposal by the UW Environmental Health amp Safety department or released into the environment Based on the written lab procedure and your actions during the lab list the identity and approximate amount mass or volume of waste that you generated while performing this experiment 05 liter of water for washing materials 100 mL of 01 M NaOH 0908 g KHP 60 mL of water 6 drops of phenolphthalein 50 mL of 01 M NaOH 60 mL of acetic acid 6 drops of phenolphthelein 1 pH strip 6 weighing paper 05 liter of water for washing down counter
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