Exam Study QuestionsChemistry 20L (Lecture 1 & 2)Winter 2004During the exam you will be allowed to use a calculator, your lab notebook, your lecture guidesand any hand-written materials that you want. The lab manual, textbooks, and other printedmaterials including the study questions and/or answers are not allowed during the exam.There is no make up for the final exam. You MUST take the exam during the lecture section inwhich you are officially enrolled. The final exam will cover ALL the topics discussed in lectures.Review the pre-lab study questions even if they were not assigned. You should be able toanswer all these questions now.Review the sidebar questions in the experiments.Review the experimental procedures.Error Analysis1. Calculate the percent error for the following quantities(a) (20.54 ± 0.02)(0.254 ± 0.003)3.21± 0.05(b) (30.078 ± 0.003) - (20.174 ± 0.001) + (9.813 ± 005)(c) [(0.642 ± 0.002) (2.413 ± 0.004)] - (0.501 ± 0.002)(d) 12.635 ± 0.005(5.967 ± 0.003) + (0.478 ± 0.004)2. Calculate the absolute errors for the quantities in question 1.3. Calculate the percent relative average deviation for the following set of data:20.96, 20.85, 20.89, 20.92Concentrations4. Define the concentration terms molarity, normality, weight percent (w/w and w/v), PPM, pH.5. When would it be appropriate to use each of the concentrations in question 1. Whatlimitations are there with any of these concentrations?6. An ethanol (C2H5O in water) solution was labeled as 1.00 x 10-3 M. What is thisconcentration in PPM, weight %, volume %? (Assume the density of water is 1.00 g/1.00mL and the density of ethanol is 0.880 g/1.00 mL.)7. A sulfuric acid solution was prepared by transferring 0.0196g of acid to a 1-L volumetricflask and diluting the solution to the mark. Calculate the concentration of acid in thesolution. in all of the units in question 5. (Assume the sulfuric acid dissociates completely.)8. A sodium hydroxide solution was prepared by transferring 0.4063g to a 100-mL volumetricflask and diluting the solution to the mark. A 10-mL aliquot of this solution was transferredto a 50-mL volumetric flask and the solution we diluted to the mark. Calculate theconcentration of the final sodium hydroxide solution in all of the units in question 5. (Payattention to significant figures. Remember the name of the flask does not designate itsprecision.)9. A student made a standard solution by transferring 0.1037g of CuSO4.5H2O into a 100-mLvolumetric flask, dissolving the salt and diluting to the mark. He then withdrew a 5-mLaliquot with a volumetric pipet and transferred it to a 100-mL volumetric flask. The solutionwas diluted to the mark and mixed well. Calculate the concentration of copper in parts permillion. Since this is an aqueous solution you can assume a mL of solution weighs 1g.10. If the tolerance of the balance is ±0.2 mg, the volumetric flask is ± 0.08 mL, and the pipet is±0.01 mL, calculate the percent inherent error in the final diluted solution.Beer’s Law11. Beer's Law is summarized by the equationA = εbcName and define each of the symbols in this equation.12. Calculate the percent transmittance of a solution if its absorbance is 0.352.13. The following set of data was obtained for the calibration curve for a Beer’s Lawexperiment.Molarity Absorbanceblank solution 0.09.80 x 10-50.2401.96 x 10-40.4753.10 x 10-40.741Plot the data.(a) Calculate the slope of the line.(b) Calculate the inherent error in the slope of this line by determining the error bars onone of the points that was used to draw the line. Assume the error in the concentration isconsistent with the rules outlined in Sec. III.1a and the error in the meter reading is ±1%(absolute) transmittance.(c) Calculate the concentration of a solution of this same compound if its absorbancewere 0.500.(d) Calculate the inherent error in the concentration determined in (c) by considering therange of possible slopes from (b) above and the error in the meter reading for themeasured absorbance of the unknown.14. (a) Hexane (bp = 68oC) and octane (bp = 125oC ) form an ideal solution. Draw the liquid-vapor phase diagram for this system. Label the axes and the phases in each area. Indicate thetemperature at which a 60% octane solution will begin to boil. What is the composition of thevapor in equilibrium with the solution?0 0.2 0.4 0.6 0.8 1.06080100120140MOLE FRACTION OF HEXANETEMPERATUREOC(b) Sketch the gas chromatogram that would result if the original mixture were separated by gaschromatography on a non polar column.(c) Sketch the gas chromatogram that would result if the distillate from the vapor in equilibriumwith the original mixture were separated by gas chromatography on a non polar column.Experiments:15. A Chemistry 20L student determined the sodium tripolyphosphate (Na5P3O10) in a detergentby ashing a sample and then titrating the acid in the ash with NaOH assuming the followingreaction:OH- + H2PO4- -> HPO42- + H2O(a) Based on the following data, calculate the percent STPP in the detergent. Molecular weight of STPP = 371 gWeight of sample 2.000 + 0.0002 gConcentration of standard NaOH 0.500 + 0.001 MVolume of standard NaOH to titrate the ashed sample 19.41 + 0.03 mL (b) Presuming that the sample was completely ashed and dissolved, and that there were noother sources of acid in the ash to react with the NaOH, calculate the percent inherenterror in the phosphate determination. Definitions16. Define the following terms being careful to identify any differences or relationships betweenthem.(a) End point and equivalence point(b) Volumetric and non-volumetric glassware(c) “Weak” coffee and “weak” acid(d) Absorbance and transmittance(e) Accuracy and precisionTechniques17, Briefly write a procedure for(a) preparating of 100-mL volumetric solution containing 1.500 g of a primary standard.(b) transferring a 5-mL aliquot of a solution using a volumetric pipet.(c) reading a buret.(d) filtering a solution using a Buchner funnel.(e) separating a mixture through distillationAcid-Base and Buffer Chemistry18. – 79. There are 62 questions relating to acid-base chemistry, buffers, and titration curves inthe chapter on Acids and Bases in the Oxtoby, Gillis, and Nachtrieb text. Thesequestions cover all aspects of the
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