Unit 14 Discussion Questions Crib

Unit 14 Discussion Questions Crib - CHEM 614 Unit 14...

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Unformatted text preview: CHEM 614 Unit 14 Discussion Questions Crib 1) A reaction: A + B C is first order with respect to both A and B and second order overall with -1 -1 a rate constant of 0.0500 M s . If the initial concentration of [A]o is 1.00 M, the initial concentration of [B]o is 0.500 M, and no product is initially present, a) What is the concentration of the product C after 2 minutes? SAME QUESTION AS #5 IN UNIT 13 b) . . . . . . . . . . . . .500 – x = ( . .500 – x = . . .500 – . .487 M = [C] )(1.00 – x) –. x c) What are the concentrations of A and B after 2 minutes? = 0.500 M – 0.487 M = 0.013 M = 1.00 M – 0.487 M = 0.513 M d) What is the concentration of the product C after 10 minutes? SAME AS QUESTION #5 UNIT 13 . . . . . . . . . . . . .500 – x = (1.53 x 10-7)(1.00 – x) .500 – x = 1.53 x 10-7 – 1.53 x 10-7x .500 – 1.53 x 10-7 = 0.500 M e) What are the concentrations of A and B after 10 minutes? = 0.500 M – 0.500 M = 0 M = 1.00 M – 0.500 M = 0.500 M 2) The reaction: 2A + 3B C is first order with respect to both A and B. When the initial -2 concentrations of [A]o=1.6 x 10 M and [B]o=2.4 x 10-3 M, and the rate is 4.1 x 10-4 M s-1, a) Calculate the rate constant of the reaction. Rate = k[A][B] k= . . . . b) What are the [A] and [B] after 4 minutes? . . . . . . . . . . . . . . . x = 8.0 =( . =. . )( . – 2.04 x 10-16x ) M = 2.4 x 1 =. – 2.4 x 1 - 1.6 x 1 M = 0.0 M M = 1.4 x 1 k1 k2 3) For a reaction that can be written as A B C the value of k1 = 5.65 x 10-3 min-1 and the time necessary to reach the maximum concentration of B is 26 minutes. What is the value of k2? . = = 26 min . . . . 0.147 – 26k2 min = . = . . . Plotting versus -3 5.65 x 10 . k2e(0.147 26k2) k2 0.124 0.00571607 0.12401 0.005715045 0.12402 0.00571402 0.12403 0.005712995 0.12404 0.005711971 0.12405 0.005710946 0.12406 0.005709922 0.12407 0.005708897 0.12408 0.005707873 0.12409 0.005706849 0.1241 0.005705826 0.12411 0.005704802 0.12412 0.005703778 you can find the value where k2 causes . to equal 0.12413 0.005702755 0.12463 0.005651773 0.12414 0.005701732 0.12464 0.005650757 0.12415 0.005700709 0.12465 0.005649742 0.12416 0.005699686 0.12466 0.005648726 0.12417 0.005698663 0.12467 0.005647711 0.12418 0.00569764 0.12468 0.005646695 0.12419 0.005696618 0.12469 0.00564568 0.005644665 0.1242 0.005695596 0.1247 0.12421 0.005694573 0.12471 0.00564365 0.12422 0.005693551 0.12472 0.005642635 0.12423 0.005692529 0.12473 0.005641621 0.12424 0.005691508 0.12474 0.005640606 0.12425 0.005690486 0.12475 0.005639592 0.12426 0.005689465 0.12476 0.005638578 0.12427 0.005688443 0.12477 0.005637564 0.12428 0.005687422 0.12478 0.00563655 0.12429 0.005686401 0.12479 0.005635536 0.1243 0.00568538 0.1248 0.005634523 0.12431 0.005684359 0.12481 0.005633509 0.12432 0.005683339 0.12482 0.005632496 0.12433 0.005682318 0.12483 0.005631483 0.12434 0.005681298 0.12484 0.00563047 0.12435 0.005680278 0.12485 0.005629457 0.12436 0.005679258 0.12486 0.005628444 0.12437 0.005678238 0.12487 0.005627432 0.12438 0.005677218 0.12488 0.00562642 0.12439 0.005676199 0.12489 0.005625407 0.1244 0.005675179 0.1249 0.005624395 0.12441 0.00567416 0.12491 0.005623383 0.12442 0.005673141 0.12492 0.005622371 0.12443 0.005672122 0.12493 0.00562136 0.12444 0.005671103 0.12494 0.005620348 0.12445 0.005670085 0.12495 0.005619337 0.12446 0.005669066 0.12496 0.005618326 0.12447 0.005668048 0.12497 0.005617315 0.12448 0.005667029 0.12498 0.005616304 0.12449 0.005666011 0.12499 0.005615293 0.1245 0.005664993 0.12451 0.005663976 0.12452 0.005662958 0.12453 0.00566194 0.12454 0.005660923 0.12455 0.005659906 0.12456 0.005658889 0.12457 0.005657872 0.12458 0.005656855 0.12459 0.005655838 0.1246 0.005654822 0.12461 0.005653806 0.12462 0.005652789 4) undergoes simultaneous radioactive decay processes: one by beta emission to produce and a second by positron emission to form . If the half life for both processes (radioactive decay processes are first order) is 12.8 years, how many g of Ni and Zn are produced in 48.5 years if there was originally 10 grams of Cu? This is a parallel reaction problem (assuming no Ni or Zn are present initially): . . = 0.0541 y-1 [B] = = . [C] = = . [A] that remains equals = (10 g) . . . . . . . . . = 4.97 g . . . . = 4.97 g = 5.26 x 10-2 g 5) Cadmium-117 undergoes beta emission with a half-life of 2.4 h to Indium-117. The Indium-117 then undergoes beta emission with a half-life of 42 m to form Sn-117, which is stable. This is a series reaction problem (assuming no In or Sn are present initially): . . . . . . a) If a sample of initially pure Cd-117 contains 1.50 x 106 atoms, how many atoms will remain after 4.00 hours? . . [A] = =. = 4.72 x 105 atoms b) How many atoms of In-117 will be present after 4 hours? . = . . . . . . . . . . = 1.83 x 105 atoms c) How many atoms of Sn-117 will be present after 4 hours? . . . . . . . . . . . . . . ...
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