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3 the handbook of chemistry and physics list the

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Unformatted text preview: 3. The Handbook of Chemistry and Physics list the enthalpy of solution of KNO3 as 34.89 kJ/mole. How does your value compare? Calculate the % er or and discuss. My enthalpy is -8.31e-3, which is entirely dif erent than the handbook relays. This may be dif erent because of our er or on the lab (I wil later explain in #4). Also, we may have mixed up data between that of KNO3 and (NH4)2Fe(SO4)2.6H2O. The percent er or is (-8.31e-6 - 34.89)/34.89 *100 = 100.0% 4. The literature value for the entropy of solution of KNO3 is 248 J/mole.K. How does your value compare? Calculate the % er or and discuss. My entropy value was completely of as wel , being -0.05 J/(K*mol). The percent er or is: (-0.05 - 248)/248*100= 100.02%. This er or is mainly due to our er or upon completion of our lab. For Part 1.C, we forgot the step of saving a KNO3 portion therefore, we are unable to obtain an accurate numerica value for the moles of Fe+ in the solution. I decided to complete the portion of the lab report as if I col ected 0.1 g KNO3. Our values for the lab there on out were slightly altered becasue we did not take into account removing parts of our products for use in part C. I am sor y for the mess up with this lab! I tried for several hours to play around with my data to bet er understand not only what I did wrong but the purpose of the lab itself. Though my data and my percetn er or may be completely of the wal , I do thoroughly understand the content of the lab. PURPOSE AND METHOD Part I We examined the method of crystalization as a purification technique. This exlpoits dif erences in solubility of comonents in the mixture. We made the sample, then cooled it in an ice bath. Afterwards, we placed them under a light for it to dry out, then measured it in a spectrophotemeter. This showed that the desired compound was crystalized, while other impurities remained in the solution. We also witnessed that solutbility changes as a funtcion of temperature. Part I We constructed an accurate solubilty curve for KNO3 by col ecting 6 data points and plot ing the curve of solubility vs temperature. We made a solution then recorded temperature as the crystalization occured. The purpose is also to conclude the enthalpy and entropy of the solution through the equation: lnKsp = -(deltaH/R)(1/T) + (deltaS)/R Does the absorbance exceed the desired range (0 to 2.0 A)? ____No________ If so, what dilution factor did you use in order to get the absorbance in the desired range? ___N/A__________ Note: Data is being restated here for ease in plot ing. For the mass of KNO3 crystal ized in crystal ization #0, the starting mass of KNO3 you weighed out in Step A.3. wil be the mass crystal ized, resulting in 100% recovery. The cel s for the mass of KNO3 crystal ized wil autofil from cel s G53, G64, and G75. The % of original KNO3 mass wil autofil from G65 and G76....
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