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Unformatted text preview: CHEM 210 .
FINAL EXAM 4/25/05
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 24.15 mL and the second after adding exactly 13.85 mL
more. Calculate the molarities of HC1 and H3PO4 in the unknown. SHOW YOUR.
WORK. (Formula weights: NaOH, 40.00 gin/mole; HCl, 36.46 gm/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 NaOI-I and the
second occmred after adding 12.22 mi more. After 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) (3) What are the strong and weak acids? strong acids: weak acids: (b) Exactly what is it about an acid that allows it to be considered “strong” or “weak”? 3. (24 POINTS) Match the following titration reactions with the plots that you would
expect each to exhibit: mLt't t
(9.5, 52) _ 025 men 5?} (f) NONE OF THE ABOVE. ' 1) 25 mL of0.10M NaOI-I with 0.10M HCl -
2) 50 mL of 0. 10M HCl with 0.10M NaOH -
3) 25 mL of0. 10M Na3P04 with 0.10M NaOH - 4) 25 mL of 0.10M NaHzPO4 with 0.10 M NaOH - 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) (3) Outline, in block diagram form, the principal components of an
atomic absorption spectrometer (AAS). ' a (b) In general, what kinds of analytes is AAS well suited for? What kind of chemical
information samples doesAAS not provide? ...
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- Spring '07