CHEM 152 Lab 4 Report
CHEM 152 Lab 4 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 1445 views. For similar materials see General Chemistry in Chemistry at University of Washington.
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Date Created: 06/09/15
Name Quiz Section ID Number Lab Partner Chem 152 Experiment 4 Thermodynamics II The Temperature Dependence of the Solubility Product Ksp pgcgg mgteggggggthis Total Points 60 5 notebook 55 template By signing below you certify that you have not falsified data that you have not plagiarized any part of this lab report ard that all calculations and responses other than the reporting of raw data are your own independent work Failure to sign this declaratbn will result in 5 points being deducted from your report score Signature DATA AND data entry 6 pts Part I Flame emission determination of K in the 050 M KCI KHP sat solution Preparation of Standards DATA Table 1 Volume of 500x10393 M needed to make Table 2 Flame Photometer Data 50 mL of each standard solution from prelab Solution Standard K M mL of stock Standard 1 750E05 1 750E05 075 2 1 2 150E04 150 3 225E04 225 4 4 300E04 300 5 375E04 375 T 050 M KCI Intensity vs Concentration 1 o O U U39I O y 102133333X 240 W O O N U39I O g 4 pts g 200 E 150 100 50 slope 102E06 M391 yintercept 24 O 000EOO 500E05 100EO4 150EO4 200EO4 250E04 300E04 350E04 400E04 Concentration Table 3 Flame Emission Determination of K in the original sample Temperature K in Dilution K in Original Solution c Measured factor M 217 4430E04 400E04 111E00 Type the calculation you used to determine K in the measured and original solutions above y 102 10quot6x 24 KA in Original Solution M Kquot in measured 2 pts Dilution Factor 450 1 02 10quot6x 24 Kquot in Original Solution M 000044350 M 111 M x 450 24 4524 4430 10quot4 M 00004 102 10quot6 102 10quot6 Part II Determination of HP39 in Saturated KHP Solutions A Standardization of NaOH Table 4 NaOH Standardization Run 1 Run 2 Run 3 Mass of KHP g Molar Mass of KHP gmol Moles KHP Initial buret volume mL Final buret volume mL Volume NaOH titrated mL Volume NaOH titrated L NaOH molesL Average NaOH 0099 M Page 1 of 5 NaOH moles of NaOH moles of KHP volume of NaOH volume of NaOH Type the calculation for determining NaOH for Run 1 0134 d KHP 20422 qmol KHP 656 10 A 4 mol 0099 M 665 mL 1000 mLL Calculate the o difference between Runs 1 and 2 lRun 1 Run 21000099 0099l 100 0 o Average Average 000665 L B Titrations of KHP Samples With and Without KCI mL of KHPaq used in titrations of Solutions 1 6 mL 3 pts Guide for completing Table 5 Move from left to right in this table entering your data and doing the calculations necessary for the next column In column C convert T to Kelvin in column F calculate mL of NaOH added in column G calculate the mmoles 10 3 moles of KHP present 1 1 reaction between NaOH and KHP so mmoles NaOH added equal mmoles of HP present in column H calculate molarity of HP from mL and mmoles in column I calculate KSp from HP in column J calculate 1T and in column K calculate In Ksp Let Excel help with the calculations enter your data for temperature and buret readings then type the necessary formulas in the first cell of each of the other columns and copy the formula to the cells below it down the column Table 5 Titration Data and Calculations for Solutions 1 6 Temperature Temperature Initial buret Final buret mL NaOH 1 Solutlon 0c K reading mL reading mL added mmoles HP HP39 M Ksp K4 In Ksp 1 03 2729 000 270 270 267E01 267E01 714E02 000367 26 2 216 2948 000 480 480 475E01 475E01 226E01 000339 15 3 334 3066 000 535 535 530E01 530E01 281 E01 000326 13 4 430 3162 000 570 570 564E01 564E01 318E01 000316 11 5 510 3242 000 605 605 599E01 599E01 359E01 000308 10 6 590 3322 000 800 800 792E01 792E01 627E01 000301 05 Type the calculations you performed for mmoles of NaOH HP and KSp for the Room Temperature solution Solution 2 mmoles NaOH mmoles NaOH mL NaOH M NaOH 480 mL NaOH 0099 M 0475 mmoles NaOH 2 pts HP mmoles of HPquot mmoles HPA 0475 mmoles of HPquot 0475 M HPquot 2 pts mL of KHP used 100 mL KHP 100 mL KHP 2 pts Ksp Ksp HPAquot2 0267 M HPquotquot2 0226 In Ksp vs lT 00 5 pts 10 y 29509x 82902 0 a g 1 5 H o 20 25 I O 30 000300 000310 000320 000330 000340 000350 000360 000370 1T slope 295E03 K R 83145 JmolK yintercept 82902 AH s m 245 As 50m 689 Type your calculations for AH and AS AH R slope 83145 JmolK 29509 K 245 kJmol 3 pts 1000 J 1 kJ 3 pts AS R yintercept 83145 JmolK 82902 689 J molK Page 2 of 5 Table 6 Replicate Titrations of Solution 2 room temperature no KCI with NaOHaq to determine H P39 this is the room temp data from Table 5 and two more replicates the room temp data from row 105 in Table 5 will autofill in the first data row in Table 6 row 168 mL of KHPaq used in titrations of Solution 2 mL autofills from cell E92 Initial buret Final buret Tem erature 39 Solution p0 reading reading mLNaOH mmOIes HP HP M Ksp c mL mL delivered present 2 216 000 480 480 0475 0475 0226 2 216 000 475 475 0470 0470 0221 2 216 000 490 490 0485 0485 0235 Average 0477 0227 Table 7 Replicate Titrations of Solution 7 room temperature in KCI with NaOHaq to determine H P39 mL of KHPaq in KCI used in titrations of Solution 7 mL Initial buret Final buret Tem erature 39 Solution p0 reading reading mLNaOH mmOIes HP HP M Ksp c mm mm delivered present 7 217 000 757 757 0749 0250 0277 7 217 000 760 760 0752 0251 0278 7 217 000 768 768 0760 0253 0281 Average 0251 0278 Type the calculations for 1 quotKSp in 050 M KCIquot using the data in the first row of Table 7 and 2 the o difference between the two average KSp values you obtained from Tables 6 and 7 ksp Ksp KA HPM 111 M 0250 M 0277 o difference IAVG Ksp KHP AVG Ksp KHP and KCII 100 0227 0278 100 224 AVG Ksp KHP 0227 RESULTS AND DISCUSSION 1 Whv did vou perform Atomic Emission Spectroscopy on the sample that contained both KHP and KCI The sample that contains both KHP and KCI has two sources of potassium ion Therefore we cannot calculate the potassium ion concentration with solely data from titrations with NaOH because the hydrogen pthalate concentration is not equal to the potassium ion concentration Instead to determine the potassium ion concentration we must use the atomic emission spectroscopy 2 What is the purpose of the calibration curve The purpose of the calibration curve is to create an equation that will enable us to determine the potassium ion concentration of the original solution using its known intensity value 3 Do we expect the two average KSp values from Tables 6 amp 7 above to be the same or different Why Discuss your results and comment the similaritydifferences between the values you obtained If the similaritiesdifferences between the values are different than expected explain possible reasons We expect the two average Ksp values from Tables 6 and 7 to be the same because Ksp is a constant and should not change unless there is a change in temperature Therefore in order to compensate for the addition of potassium ions in the KCI KHP solution we expect a decrease in HPquot concentrationHowever in contrast to this expected value with the addition of a common ion we obtained an increased Ksp A possible reason for this increased Ksp is a human error that could have occured in the section of the experiment involving the flame photometer The specific human error that could have given us a higher solubility product is the mistake of emersing the pipet too deeply into the beaker with the sample and getting a saturated solution with KHP crystals This is consistent with the calculated potassium ion concentration which was above 1 M a molarity that is impossible 4 Based on your results at room temperature what is the solubility of KHP in gL Ksp 0227 10 HP 2 xquot2 x 0476 M 0476 moiL 0476 moiL 20422 gmol 973 gL Page 3 of 5 4 pts 2 pts 2 pts 2 pts 2 pts 2 pts 2 pts Page 4 of 5 5 What will happen to the solubility and KSp when NaOHaq is added to a satuared solution of KHP Explain your reasoning Assuming the temperature remains constant Ksp will remain the same As a strong base is added to the saturated solution the hydrogen phthalate will act as an acid and react with the NaOH to create water Therefore the hydrogen pthalate concentration will decrease To compensate for this decrease in products hydrogen phthalate concentration according to Le Chatelier39s principle more reactants will be changed in to products As a result the solubility will increase 6 What will happen to the solubility and KSp when HClaq is added to a saturated solution of KHP Explain your reasoning Also assuming the temperature remains constant Ksp will remain the same As a strong acid is added to the saturated solution the hydrogen phthalte will act a base and react with the HCI to create water Similarly the hydrogen phthlate concentration will decrease To compensate for this decrease in products hydrogen phthalate concentration according to Le Chatelier39s principle more reactants will be changed in to products As a result the solubility will increase 7 Consider the following typical results AH S In 341 kJ mole and the AS S In 120 JKmole How do your results compare Calculate difference and explain possible reasons for differences 245 34 282 689 120i 426 341 120 For the enthalpy of the solution I there was a percent difference of 282 percent and for the entropy of the solution I there was a percent difference of 426 percent Possible reasons for this drastic percent difference is over titration of NaOH which frequently occurred in our experiment and the decreasing temperature of a solution as it is being diluted and titrated As the KHP sample is diluted with DI water the temperature of the sample decreases Because the temperature decreases also as it is being titrated with NaOH the Ksp probably decreased alsogiving us values of Ksp that are actually lower than the theoretical expected value Laboratory Waste Evaluation 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 15 mL of 00050 M KCI 250 mL of DI water 1 mL of 05 KCI KHP saturated solution 100 mL of DI water 240 mL of 01 M NaOH 30 mL of DI water9 drops of phenolphtalein indicator solution 030 grams of KHP 880 mL of 01 M NaOH 8 mL of prepared sample KHP solutions 160 mL of DI water 24 drops of phenolphtalein 9 mL of KCI KHP solution 240 mL of 01 NaOH 9 drops of phenolphtalien Page 5 of 5 2 pts 2 pts 2 pts 1pt