ex-final-s06

ex-final-s06 - Chem 104 section 1, Final Exam Friday May...

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Unformatted text preview: Chem 104 section 1, Final Exam Friday May 12, 2006 Your section's TA 1. For optimum results show your work. Put your answers in the little boxes provided. 2. A page labeled "Scratch" has been appended to the exam. It may be used for scratch calculations and doodling but will not be graded. 3. Indicate your answer clearly. A question with more than one answer gets graded in an arbitrary manner. 4. Don’t draw awful structures with dangling valences etc. Remember: when you draw a structure you're making a statement. 5. For maximum clarity draw structures as "CH3CH2.." or “CH3-CH2-“ rather than line structures, although the latter will be accepted if correct (by our criteria). 1. (10 points) We wish to prepare 600 mL of a water solution of Al2(SO4)3 with the requirement that the aluminum ion concentration be 1.3 molar. How many grams of aluminum sulfate do we need? grams 2. (5 points) Draw the structure of the amino acid plx tyrosine. Draw the neutral uncharged form, not the zwitterion. 3. (10 points) Sodium phosphate reacts with aluminum chloride to afford a precipitate of the insoluble salt aluminum phosphate (AlPO4). Write and balance the equation for this metathesis reaction. eqn 0 4. (25 points) Consider the structure of the chemical warfare incapacitating agent "82" -) 0 0H a. How many sp hybridized atoms are present in this molecule? 0 0 #sp N 82 war gas b. How many sp2 hybridized carbon atoms are present? #spZC c. How many sp3 hybridized carbon atoms are present? I w "d w d. What is the molecular formula of 82? fml e. What is its molecular weight (to the nearest tenth g./mole)? mwt 5. (20 points) "Draw the structure of..." In each of the parts below draw the structure of a chemical compound that has the stated properties. 5a. A product arising from dibromination (Br2/hv) of n-octane that has no methyl groups as part of its structure. 5b. A product arising from dibromination (Br2/hv) of n—pentane that has two ethyl ("CZH5-") groups as part of its structure. 5c. A hydrocarbon C7H12 that does not react with H2 in the presence of Pt. 5d. That product C5H11Br that arises from bromination of n-pentane and is chiral. 6. (10 points) Circle that compound below 0 0 which gives on dehydrating "condensation" the o E polymer shown 9. 0 CW M O 5: OH H HO WV” 7a. (10 points) "White phosphorous" is one of the allotropic forms of the element phosphorous. It has the formula P4 and burns vigorously in air to form its oxide P205. Write and balance the equation for this reaction. eqn 7b. (5 points) True or false (right minus wrong, so leave it blank if you're not sure): "From inspection of the balanced equation above it follows that the rate of this oxidation reaction is first order in elemental phosphorous 7c. (5 points) True or false (right minus wrong): "From the balanced equation above: the equilibrium constant for this reaction is Keq=[P205]2/ ([P 4110215)." 8. We study the kinetics of acid catalyzed hydrolysis of the dipeptide glycyl glycine (C4H8N203) in water containing hydrochloric acid. 8a_. (10 points) Write and balance the equation for this reaction. You may use either structural or molecular formulas. balanced eqn Working like third-level demons, we gather kinetic data on this hydrolysis that are summarized in the following table: rate, “glycineydt, M min-1 [dipeptide], M [hydrochloric acid], M 4 3.35*1o‘5 4.37*10'3 5.03"10'3 4.22*10‘3 8b. (15 points) From the data in the table immediately above, what is the kinetic order in each reactant (phrased like "first order in chloride ion.") Be concise but intelligible. order in peptide order in acid 8c. (10 points) What is the rate of this reaction (specify units) when both peptide and hydrochloric acid are one molar? rate 9. (20 points) Valeric acid (CH3CH2CH2CH2C02H) is responsible for the pungent aroma of the plant Valerian. It has the pKa of 4.58. What is the pH of a 0.300 molar solution of this smelly stuff? pH 10. The common radioactive isotope of sulfur, so-called "3-35", decays by emission of a beta particle. its half life is 87.2 days 10a. (10 points) Write and balance the nuclear equation for this decay process. Use the correct nuclide notation. eqn 10b. (15 points) (A shaggy guinea pig story) We raise a guinea pig on radioactive guinea pig food. The food contains radioactive sodium sulfate ("S-35", 4.6 * 105 counts per minute per gram of food. At maturity, after feeding a total of 4.5 kg of radioactive food, the guinea pig's tail is removed. It weighs 3.55 grams and is radioactive ("S-35", 4700 counts per minute (cpm)). How radioactive will our (actually the guinea pig's) tail be (in cpm) after one year? - 11a. (10 points) We prepare an "valeric acid buffer" containing 0.15 molar valeric acid (pKa 4.58) and 0.1 molar potassium valerate in water. What is the pH of this solution? - 11b. (10 points) To 100 mL of this buffer we add 8.0 mL of 0.32 molar hydrochloric acid. What is the resulting pH? - ...
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ex-final-s06 - Chem 104 section 1, Final Exam Friday May...

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