Physical Chemistry I&II- Lab Report
Physical Chemistry I&II- Lab Report CHM 4410
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Date Created: 10/10/15
Experiment 1 Sucrose Inversion by The Acid Catalysis HCl and Monochloroacetic Acid MCAA Physical Chemistry II CHM 4410C Sec 10127 Mon J isun Ban February 22 2015 Abstract Enzyme catalyzed reaction is really important in biochemistry field An enzyme speeds up the rate of the reaction and in physical chemistry we can calculate the rate of the reaction and determine the activation energy In this eXperiment we are using D Sucrose to react with two different acids at different temperatures Sucrose has the property of dextrorotatory and it rotates aroun glmplane of polarimeter in a clockwise rotation H2W len it reacts with an acid it O the property of laevorotat y B rformnigOEcHe nt we toseldtl iph de rmined its ate 0 I e lstibi e 39B39y39plott gdhe Arr nius39equat n thela ti ation eHQr dOto b lI ZElllO3kJmol HO OH HO CHEOH OH OH OH OH Introduction Sucrose Glucose Fructose Regards to chemical kinetics the rate of enzyme catalyzed reactions is the most important topic that is being studied Enzymes are the catalysis of a biochemical reaction which helps the proteins to perform its reaction faster In physical chemistry the rate of the reaction of a substrate and enzyme can be determined by changing the environment and observing its physical properties Environmental changes are the temperature pressure color or change in pH of its surrounding Physical properties that we can observe is change in color pH of the compound or its angle of rotation of polarized light which is used in the experiment Sucrose sugar is used in the eXperiment which has the dextrorotatory D sucrose has the property of clockwise rotation of the polarimeter Once D sucrose react with an acid at a certain temperature over time it forms a product with the property of counter clockwise rotation of the laevorotatory fructose The reaction is shown in Figure 1m Figure l Sucrose reacting with an acid it undergoes condensation and forms D glucose and L fructose Mechanism of Michaelis Menten allows us to assume that the intermediate of this reaction ES is formed and then reacted to produce glucose and fructose The derivation of the sucrose eXperiment involving Mechaelis Menten equation follows K1 Eenzyme S substrate K1 ES quot K2quotgt E Pproduct 1 d sucrose Rate dt K1sucrosequotHy 2 d sucrose Keffect K1HY I d Keffecdsucroselquot 3 sucrose C where C is the concentration of the sucrose and Keffect is the effective rate constant of sucrose Equation 3 has been integrated and simplified to K effect t CC 6 4a 1 L n C o quotKeffect Effective rate constant of sucrose can be determined when the experimental data of the rotational angles are plotted K effective is the slope of the graph The concentration of the sucrose is proportional to the rotational angle by some constant A on 2 AC During the reaction aAS sucrose glucose AF fructose a and at time infinity X00 glucose AFFfructose We can come to a conclusion for the reaction that the initial concentration of the sucrose is equal to the concentration of glucose infinite and to the concentration of fructose infinite X00 AG 0 sucrose By manipulating equations 56 we can form an equation that will give us the changes in rotational angle of the reaction Xe X00 A5quot AGquot osucrose C0 sucrose Kt X00 A8quot AGquot AFCtsucrose Ct sucrose The ratio of equation 7a and 7b can be related to equation 4b Taking a natural log on to both sides we get OO O X o x gt 1n C 6 quotKeffect 7C The equation 7c can be re written in the form of ymXb 1n fat X00 quotKeffect 1n fa XOOgt 8 The equation 8 is in a form of the slop intercept equation and which can be determined when the data of the rotational angles are plotted This equation is for the first order reaction The slope K can be used to find the activation energy of the reaction Ea K A e 9 Where A is the constant Ea is the activation energy R is the gas constant and T is the temperature in Kelvin The purpose of this experiment was to measure the constant K order and activation energy By usin a polarimeter and recording the rotational angles of sucrose reaction with two 39 V lyadrgcehlogipvagigraql and monochloroacetic acid MCAA at different temperatures Q can emua t astga stant K ordek g ragg gg energy 2 E e m j if Nicol prism Nico t quot 39 Y f 7 Sample tube a Experlg eh 7 c l 739 7 p k of t eisolutionsiwerge made to begin the eXpErimentWJQD 4M HCl 100mL of 4M m ochloroacetic acid MCAA and 250mL of 05 S rof sucrose 32 plastic bottles were cl 1 eight bottles of AA and sixteen bottles of sucrose were made Four different temperature baths were set so that the solutions would equilibrate at a desiring temperature Four of the MCAA and sucrose stocks were placed in the 50 C bath Other four of the MCAA and sucrose stocks were placed in 60 C bath Four of the HCl and sucrose stocks were placed in the 30 C bath and the rest of them in the 40 C bath Four stocks for each temperature were run to take the average polarimeter reading Figure 2 shows the setup of the polarimeter Figure 2 Sample tube is where the solution is poured into and with the light we can observe the rotational angle We are looking for an angle that gives us an equal shade like a After the solutions has been equilibrated at the desiring temperature sucrose and an acid was mixed and poured into a polarimeter sample tube Carefully without creating any bubbles the solution was transferred into the sample tube and the angles of rotation was read Once the polarimeter reading has been recorded it was placed back into the plastic bottle and to the same temperature bath for another 10 minutes The eXperiment was repeated until the negative angles of rotation was read The solution bottles were stored for a week and the rotational angle at time infinity was measured Result Discussion With all the data collected the equation 7c was used and graphs were plotted The Table l is the data of change in rotational angles of the sucrose with 4M of MCAA in 60 C Almost 2 hours was required for the complete reaction of sucrose to form the product of counter clockwise rotation For each reaction 4 trials were run and its average was taken into the calculation Table 2 is the X and y coordinate it was calculated using the equation 7c and this table includes the graph s slope and its error propagations Table 1 through Table 8 is in the same format Table l M 34A 60 C Time SampleA B C D Time Optical Std dev minutes minutes Rotation avg 0 1260 1250 1260 1300 00 127 02 10 1050 1110 1090 1090 100 109 03 20 950 920 1000 950 200 96 03 30 820 840 8 20 660 300 79 08 40 630 560 590 550 400 58 04 50 5 10 480 460 470 500 48 02 60 410 340 380 360 600 37 03 70 300 290 290 260 700 29 02 80 210 220 230 190 800 21 02 90 140 140 130 110 900 13 01 100 040 040 020 010 1000 03 02 110 050 040 040 030 1100 04 01 In nity 3 75 3 85 4 10 360 In nitv 38 02 Table 2 MCAA60 C Time m39nutes In 0mg Xinf 0 280336 10 268615 20 259339 30 245745 40 226696 50 215466 60 202155 70 189837 80 178339 90 163413 100 141099 110 a 123110 300000 250000 200000 c39linr quotE 150000 In a3 100000 050000 000000 IJ NEST slope K 140E02 standard error 3 55 EM correlational coefficient 9 94 EOl 2 8495 0 0231 0 0425 Time 05 lrlrrdwg aim MCAA 609C 1 0014x l 28495 F112 09936 0 20 40 60 80 Time minutes 120 Graph 1 This is plotted using Table 2 and slope indicates the K effective according to the equation 8 K effective is 0140 The rotational angle of sucrose reacting with 4M of MCAA under 50 C is shown in Table 3 This group ran out of time during the experiment and had to stop after an hour of taking the measurement Even though we do not have the data points up to the negative rotation we can assume that the same concentration of MCAA at a lower temperature the rotational angle changes slightly slower than the 60 C Table 4 shows the same data as the Table 2 but it is for the MCAA under 50 C Table 3 M 34A 50 C Time SaraneA B C D Time Optical Std dev rrinutai minutes Rotation avo 0 1185 1170 1246 1235 0 1209 04 10 1020 10 20 1080 1080 10 1050 03 20 805 900 904 914 20 881 05 30 784 782 720 745 30 758 03 40 585 554 620 610 40 592 03 50 519 490 500 478 50 497 02 60 410 405 395 375 60 396 02 In nity 388 395 367 385 In nitv 384 01 Table 4 MCAA 50 C IJ NEST 39 In or a me mums avg mi slooe K 121E02 27775 0 276805 standard error I I 236EO4 00085 10 2 66288 correlational coef oent 9 98 E01 00125 20 253726 30 243493 40 227829 Time 05 In Draug aw MCAA 50 C 300000 l 250000 39 4 200000 39 quotifquot E H g 150000 5 v 00121 27775 5 02 09981 100000 050000 000000 0 10 20 30 10 50 00 70 Time minutes Graph 2 This is plotted using Table 4 and slope indicates the K effective according to the equation 8 K effective is 0121 Sucrose was reacting with HCl at a lower temperature than the MCAA Because HCl is a strong acid it is more likely to readily react Compared to MCAA HCl required very little amount of time As it is shown on Table 5 about only 30 minutes were required for the sucrose to completely react The sampleA for the HCl 30 C was omitted because the sample spilled during the first reading Table 5 HO 30 C Time Sample B C D Time Optical std dev minutes A minutes Rotation 0 43 91 9 68 65 10 97 0 852 150 10 05 06 05 05 1 1 1 1 10 072 030 20 17 16 26 25 17 15 20 193 048 lnfinitv 4 39 41 41 41 4lnfinitv 403 008 Table 6 3mm Time us In um a nf HCI 30 250000 H 200000 5 150000 a 5 100000 0089425038 v 02097395 050000 000000 0 5 10 15 20 25 Time minutesl Graph 3 This is plotted using Table 5 and slope indicates the K effective according to the equation 8 K effective is 0894 Table 7 and Table 8 shows HCl 400C data We can definitely assume that the stronger acid at a higher temperature will react faster This experiment only took 2 data points for the rotational angle to reach in negative angle Table7 HG 40 C Time Sample B C D Time Optical std dev minutes A Rotation avg 0 35 35 34 08 08 07 24 27 28 43 44 44 0 281 14 10 394 4 39 29 32 28 3 32 33 36 35 35 10 340 041 In nitv 4 4 41 39 38 4 4 4 41 39 4 41n nitv 399 009 Table 8 Time US In am aim HCI 40 C 12 1D 8 u 4 fZ SJ ggl Kl 10 2 R2 1 U g l 15 1 15 2 25 Time minutes Graph 4 This is plotted using Table 6 and slope indicates the K effective according to the equation 8 K effective is 5493 From the data we were able to calculate the rate constant K Using the equation 3 the rate constant was calculated For the H since the MCAA is a weak acid using its Ka value the hydronium concentration was calculated For HCl because it is a strong acid it dissociate 100 therefore its hydronium concentration is 2M Table 9 shows the calculation of the rate constant K Using the calculated value from Table 9 we can plug into an Arrhenius equation and plot Graph 5 Table 10 is the calculation of the activation energy of the sucrose Table 9 Kaome l35EO3 Rmo K 8314 MCAA 4 HO Mi 4 Mi MCAA 00728 040 HO 2 MCAA50 MCAA60 Ho 30 H0 40 Kerr 0 01206 0 01402 0 08939 0 24474 JlT 000309 000300 0 00330 000319 Kkp m iHi K 0 16561 0 19257 004469 0 12237 InK l79810 l64728 3 10790 2 10071 Arrhenius IN US nK 000000 000295 000300 000305 000310 000315 000320 000325 000330 000335 050000 100000 150000 InK 200000 250000 300000 393 25806 2134 H1 09398 350000 400000 1f39T Kelvin Graph 5 The Arrhenius graph was plotted based on the Table 9 and from the slope we can calculate the experimental activation energy of the sucrose F39 Table 10 Ac va mBBWEaernlltA In K EaR1m nA Avtica on energy Ea In DI 9J8E02 Conclusion IJ NEST slope EaRl 7 581 El03 2135El01 standard erro 14 El03 4 3 EIOO correlational coefficient 09398 03003 The literature value for the activation energy of sucrose is 1092kJmol 3 The experimental activation energy is 9118E 1 kJmol The percent error is almost 100 and it is probability because of the experimental error that occurred during the lab The sucrose solution and acid solution might not have been mixed evenly where we get different rotational angles Especially for the HCl experiment the rotational angle was different between the samples Next time we can thoroughly mix the solution before performing any measurement and to make the concentration of the solution more precisely Reference 1 Shoemaker D amp Garland C 2003 ltigtEXperiments in physical chemistryltigt 8th ed pp 271 2882 New York McGraw Hill 2 Troendle R 2015 Sucrose Inversion Lab https blackboardunfedubbcswebdaVpid 3 101 893 dt content rid 219199061courses2015SPRINGCHM441 1C 10121 02MULTISucrose20Handout 28129pdf 3 Tombari E Salvetti G Ferrari C amp J ohari G nd Kinetics And Thermodynamics Of Sucrose Hydrolysis From Real Time Enthalpy And Heat Capacity Measurements The Journal of Physical Chemistry B 1113 496 501 Experiment 2 Absorption Spectrum of Conjugated Dyes the particle in the boX Physical Chemistry II CHM 4410C Sec 10127 Mon J isun Ban March 22 2015 Abstract Conjugated dyes Amax was observed and calculated by using the Kuhn s assumption The one dimensional particle in a box concept is applied to the experiment where the conjugated dyes H electrons are represented as particles in a box Although the Kuhn s model does not agree precisely to all conjugated dyes it is a useful model for the greater electronegative elements contained dyes The stronger the electronegative element contained in the dyes the potential energy rise sharper creating the sharper wall Our correction factor CL value was calculated and it was in the range of O20 to 158 The correction factor was smaller for the conjugated dyes with the stronger electronegative element Introduction Experiments in Physical Chemistry by Garland et al states that the spectrum s visible region of the absorption bands are related to the energy of the transitions from the ground state of a molecule to an excited electronic statem The energy is from 170 to 300 k mol39l but the lowest excited electronic state is more than 300 kJ mol391 in many substances therefore no visible spectrum is observed For the compounds that will be used in the experiment they are colored which can be absorb in the visible spectrum We will be analyzing several symmetric polymethine dyes with the UV spectrometry which in general have some weakly bound or delocalized electrons e g free radical or H electrons The particle in a box model concept is used as a model in the experiment 2 In quantum mechanics the energy change for the transitions can be modeled as the following 3 hzn2 E 8ma2 qu 21 where h is the Planck s constant 11 is an integer 123 n m is the mass of the electron and a is the length of the box The transition of an electron from the ground state to the excited state is denoted as 3 AE hz qub The number of electrons in any given energy is limited to two by the Pauli Exclusion Principle When the molecule or the ion absorbs light it associates with the ground state energy levels as N2 where the N number of H electrons and the lowest empty level as N2 1 The energy change for this transition can be written by plugging into an equation la 1 h2 8ma g 2x AE N1 2 Eq2 Since we are looking for the Amax we want to rearrange the equation as Eq 3 8mc a2 2x h N1gt Eq3 According to the Garland et al Kuhn s model relates a to the length of the box to the number of carbon atoms in a polymethine chains 1 a p3l N p3 Finally the equation is rearranged to Eq 3 2x8mc h ltltP3lgt2 w lteq where p is used as the number of carbon atoms in the conjugated chain 1 is equal to a constant which is 0139nm Once we combine all the constant terms it is simplified to 637 A24637M 4 Eq5 With the assumptions from the Kuhn this equation allows us to calculate the expectation Amax Without the Kuhn s assumption the conjugated dyes have the polarized molecules at the ends of the benzene rings These polarized groups represents that the potential energy are not rise as sharply at the ends therefore a correction factor a is implied to the Eq 5 yielding Eq 6 A637 Eq6 The correction factor Alpha on can be calculated by the average Amax from the experiment Experimental method To find the Amax of each conjugated dyes the solutions were made in a small volumetric ask The dyes were in the powder form and very little amount were used to make the solution with methyl alcohol The dyes are toxic and degrades in the light so they were handled carefully The concentration or the volume of each dyes did not matter because we are only trying to find the wavelength at the peak the maximum absorbance The dyes were prepared enough so that filled the cuvette Total of nine different dyes were used in this experiment When setting up the UV Spectrometer set UV Visible ranges from 390 to 760 for 3 cycles We want to make sure it does not read too fast so set the speed at 120 nmmin and the slit width as 05nm Blank the UV Spectrometer without anything placed inside then when is done place the cuvette with the methyl alcohol reference on the back and the solution on the front The Amax from the wavelength at the peak in the spectra of each dye was recorded Result Calculations Wavelength vs program Figurel absorbance of a conjugated dye was graphed by the UV Spectrometer Figure 1 13 g 12 11 l 39139 1 0 fl 1K 09 t 39 08 f 07 06quot x 05 r l x 04 x N 03 amp 02 5 r 5 e d 03917 Carbon Eeclrors Ag u u 7 31 ex p 7563 E4152 nm NI I a n Description chdllute plnl ggpleCycle1 11W 5227329 5227248 5227619 5227399 3 6 32760 5957 HacJN N CH3 397 J 1 i lFig e shows ea h Ui ea ergg s f Ll use4g l gs hg2 49 the error between the measured and the expected values J r H3C CH3 11W 6994008 6995171 6992428 6993869 7 10 57909 2077 figure Ange 5566264 5567346 5567722 5567111 5 8 45298 2290 6512666 6512627 6512963 6512752 7 10 57909 1247 7582218 758 5853 7583524 7583865 9 12 70560 748 7 39 39 4823104 4824771 4824192 4824022 5 8 45298 650 CNACHg 39 chAN GLOWltOQ 39 39 l 5792461 5793018 5792358 5792612 7 10 57909 003 0M 33cietl39nllo ricabooHinencide 6821899 6821766 6821287 6821651 9 12 70560 332 By using the experimental A we can calculate backwards to find the correction factor 0t from the Equation 6 Figure 3 shows the each step of the calculation and the correction factor or Figure 3 Avatar L Al I 39 a quot39Lltm4gt PAT m3 1 Tammi zgm39m 8 21 5744 758 15792 942 8479 921 1 2082 1098 12077 1099 09897 8 74 7866 887 08688 1022 11247 1060 06050 1191 15477 1244 04408 W 7 57 6816 8 26 02557 A Q Ll U I f 5 if IQ IAK f f LIA 0 f 3339cie M0dricabooaineiocide 1071 13922 1180 0 2010 Discussion Conclusion Smaller number of carbons represented in a conjugated dye the higher the error was Since the expected value was an assumption from the Kuhn s model the correction factor was not included in the calculation Therefore the experimental and expected values did not agree I was able to see that the value of error decreased as the carbon number increased The Am was greater for the longer carbon Chained dye Analyzing the correction factor on the less electronegative element presented in the structure alpha value was greater Sulfur is less electronegative than Oxygen therefore those conjugated dyes have greater alpha values In conclusion of the data the greater electronegative element presented in the molecule will encounter with Kuhn s model better Because the Kuhn s model assumes that the potential energy on both ends of the molecule rise sharply and alpha as 0 The experiment was successfully done The calculated correction factor values are in between 020 to 158 Also during the experiment even though we made the solution using DI water for the first set of the dyes the sample dissolved well We found out that using the solvent as DI water or methyl alcohol did not really matter Unless the solution dyed into the cuvette which affected the second solution s data by giving us two different peaks The cuvette was easily Cleaned with the methyl alcohol Overall experiment was successfully done Reference 1 Shoemaker D amp Garland C 2003 ltigtExperiments in physical Chemistryltigt 8th ed pp 393 398 New York McGraw Hill 2 Engel T amp Reid P 2006 Pi Electrons In Conjugated Molecules Can Be Treated As Moving Freely In a Boxquot In Physical chemistry 3rd ed pp 347 348 San Francisco Calif New York Pearson 3 Troendle R 2015 Absorption Spectrum of Conjugated Dyes the particle in the box httpsblackboardunfedubbcswebdavpid 3 1 1 1044 dt Content rid 222174751Courses2015SPRINGCHM441 1C 10121 02MULTIThe20energy 200hange2028CE94E2920for20electron20transitions20modeled 2020from20the20quantum20mechanical20description200f20the 20particle20in20a20box Handoutpdf
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