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Unformatted text preview: Group Work 2, CHM 152, Burk, Names: ______________Key____________________ due 2-13-09 3pm
Papers will NOT be accepted after 3pm because I need to post the
key so you can study for the exam over the weekend.
1. Consider the following mechanism:
elementary step one:
elementary step two: H2O2(aq) + I-(aq)
H2O(l) + OI-(aq)
H2O2(aq) + OI (aq)
H2O(l) + O2(g) + I-(aq) a. What is the intermediate? ____ OI-(aq)_______
b. What is the catalyst? _______ I-(aq)________
c. What is the overall reaction? 2H2O2(aq) 2 H2O(l) + O2(g) d. What is the molecularity for step one? ________bimolecular______
e. What is the molecularity for step two? __________ bimolecular___
f. If the real rate law is rate = k[H2O2][OI-] then which step is rate determining? ___Step two_____
2. Circle true or false.
a. Most collisions results in product formation. True False b. If the [reactant] increases, the rate increases. True False c. If the collision energy is greater than the activation energy, products always will form. True False
3. The activation energy for a reaction is 106 kJ/mol. At 298 K the rate constant is 3.46 x 10-5 s-1. At what
temperature is the rate constant 9.63 x 10-5 s-1? Show your work and circle your answer.
a. 0.305 K b. 305 K c. 328 K d. 829 K e. 291 K 1
3.46 x 10
9.63 x 10 5s
5s 1.024 1
1 106000 12749.6 0.0000803
0.00328 1 8.314
298 4. What is the name for a positive electron? ______positron_________
5. What exactly is an alpha particle made of? helium nuclei (2 neutrons & 2 protons) 6. Americium-241 is used in smoke detectors and it is an alpha emitter. Write the alpha decay reaction. 7. Write the beta decay reaction for strontium-90. 8. Write the positron decay reaction for iodine-124, which is used in therapeutic PET scans. 9. Write the electron capture reaction for aluminum-26. 10. Fill in the blank. 23 11Na + _____ 11. Fill in the blank. 59 27Co + 1 0n 24 ______
56 25Mn 11Na + ____ + 1 1H _______ 12. Magnesium-28 has a half-life of 21.0 hours. How much of a 34.5 gram sample would remain after 4.00
days? Show your work.
2 ⁄ 96
21.0 34.5 . . 34.5 0.0421
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