210finala - CHEM 2 l 0 FINAL EXAM 1 1/28/05 NAME: 1. (30...

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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 NaOI-I - 4) 25 mL of 0. 10M NaI-I2P04 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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210finala - CHEM 2 l 0 FINAL EXAM 1 1/28/05 NAME: 1. (30...

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