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Unformatted text preview: CHEM209
Final Exam
10/3/05 NAME: 1. (20 POINTS) Suppose a student is determining the total base content of an antacid
tablet by performing a back titration. He/she weighs out a 0.3022gram portion of a tablet
whose total weight is 1.6335 grams, dissolves this in exactly 30.00mL of deionized ‘
water, and then adds exactly 20.00 mL of 0.1 000M HCl in order to bring the pH down to
2.2. This solution is then carefully backtitrated with 0.1050M NaOH, with 3.77 mL required to reach the equivalence point. Calculate the total base content (i.e., the number
of moles of base contained) of the antacid tablet. SHOW ALL WORK CLEARLY,
(Formula weight of HC] = 36.46 gram/mole; formula weight of NaOH = 40.00 gram/mole). 2. (30 POINTS) (:3) Write the equation for Beer‘s Law and deﬁne all the terms
(inctuding the correct units for each term). (b) The absorbance of a 1.0 x 10‘5M Fe(1,10phen)32+ solution is measured at a
wavelength of 510 nm and found to be 0.400. What is the transmittance of this solution? SHOW YOUR WORK. ——_———'——me m..._._,.,.__....__.._.____..,....m... , . (0) Suppose the solution in part (b) is diluted with deionized water by a factor of 2.
What are the absorbance and transmittance of the diluted solution? SHOW YOUR WORK. 3. (14 POINTS) Sketch the shape of the titration curves expected for the following
titrations: r (a) BC] with NaOII
pH
. mL NaOH
(b) KHP with NaOH
mL NaOH 4. (16 POINTS) What quantities are plotted on the x and yaxes of:
xaxis axis
(a) a chromatogram? (b) a calibration curve? ....._....__..__..,._,.._....__.._..H..‘M._mrw’mr 7w , A. 5. (10 POINTS) Deﬁne the term “retention time”. What is its principal use in GC
analysis? 6. (10 POINTS) Write the equilibrium constant expressions for the follOwing balanced
chemical reactions: . (a) 2Mn04' + 5H3As03 + 6H“ ———.> 2Mn2+ +5H3AsO4 +3H20 K . Ag2304 ¢(solid) —~—+ 2Ag+ + 30.;2 _ ____..__._.__.__...u._..u.._. “WWW...” ...
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 Spring '07
 Greg
 Equivalence point, total base content, CHEM209 Final Exam

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