Question

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Experiment 14 - Nuclear Chemistry iven 0.050 mg of technetium-99m, a radioactive isotope with a half. 5. A patient is given 0.050 mg of technetium-99m, a radioactive life of about 6.0 hours. How much technetium will remain after 24 hours hours? after 24 hours? After 48 6. A patient receives a 58-mg dose of 1-131 to obtain an image of her thyroid. If the nuclide has a half-life of 8 days, how long will it take until less than 1 mg of I-131 remains in her body? 7. One of the nuclides in spent nuclear fuel is U-235, an alpha emitter with a half-life of 703 million years. How long would it take for the amount of U-235 to reach one- eighth of its initial amount? 8. Polonium-218 is an alpha emitter with a half-life of 3.0 minutes. Estimate how long it will take for a 312 g sample of polonium to decay to less than 1 gram?

Answer 1

5. Half life is the time when the initial concentration reduces to half. There are 24/6 = 4 half lives in 24 hours.

[A] =[A0] (1/2)^n = 0.05*(1/2)^4 = 0.0031 M

Concentration after 24 hours = 0.0031 M

There are 48/6 = 8 half lives in 48 hours.

Concentration after 48 hrs = 0.05*(1/2)^8 = 0.00019 M