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Unformatted text preview: CHEM 2 l 0
FINAL EXAM 1 1/28/05
NAME: 1. (30 POINTS) (a) Suppose that you are using 0.100M NaOH to titrate a 20.00 mL
solution that contains an unknown mixture of HCl and H3PO4 and that you obtain two endpoints  the ﬁrst after adding 20.15 mL and the second after adding exactly 10.85 m1,
more. Calculate the molarities of HCl and H3P04 in the unknown. SHOW YOUR WORK. (Formula weights: NaOH, 40.00 gm/mole; HCl, 36.46 gin/mole; H3PO4, 98.00
gin/mole) (b) When performing this experiment, a student analyzes his/her titration plots and
concludes that the ﬁrst equivalence point occurred after adding 5.50 ml of NaOH and the
second occurred alter adding 12.22 ml more. Aﬁer lab, he/she asks the professor to “check the results”. Without even using a calculator, the professor sadly informs the
student that these results are not possibly correct and that this experiment will undoubtedly need to be repeated. Brieﬂy but clearly explain how the professor was able
to reach this conclusion. 2. (20 POINTS) 20 POINTS) Show clearly how you would prepare 100 ml of a 25 ppm
K solution from: a) a 500 ppm K stock solution. “W—meh
........_......__..u—————qr—— I b) solid KC! (formula weight of KCl = 74.55 gin/mole; atomic weight of K = 39.10
gm/mole; atomic weight of C1 = 35.45 gin/mole). 3. (24 POINTS) Match the following titration reactions with the plots that you would
expect each to exhibit: (a) (b)
PH pH
mL titrant mL titrant
(c) ((1)
pH pH
ml, titrant mL titrant
(e) (f)
NONE OF THE ABOVE
pH
mL titrant 1) 50 mL of0.10M NaOH with 0.10M HCl «
2) 25 mL of 0.10M HCl with 0.10M NaOH 
3) 25 mL of 0.10M Na3P04 with 0.10M NaOII  4) 25 mL of 0. 10M NaII2P04 with 0.10 M NaOH  ____m]____.m__t_m~______]____ﬂmmm__m_.._. 4. (20 POINTS) What is the Nemst equation? Deﬁne all terms (including units). 5. (28 POINTS) (a) Outline, in block diagram form, the principal components of a gas
chromatography (GC) instrument. (b) In general, what kinds of analytes is GC well suited for? For what kinds of samples is
GC not well suited? 6. (28 POINTS) (a) Outline, in block diagram form, the principal components of an
atomic absorption spectrometer (AAS). (b) In general, what kinds of analytes is AAS well suited for? What kind of chemical
information samples does AAS not provide? ...
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 Spring '07
 Greg

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