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The half-life for electron capture for 10K is 1.30 ~ 109 years. What percent of the...
70. The half-life of cobalt-60 is 5.3 years. What percent of a sample of cobal:-60 will remain after 21.2 years? A) 50% B) 40% C) 12.5% D) 10% E) 6.25%
Uranium-235 has a half-life of 7.04 x 108 years. How many years will it take for 99.9% of a U.235 sample decay A. 7.08 105 yr B. 1.0 x 106 yr C. 4.7 x 10º yr D.4.9 x 109 yr * E. 7.08 109 yr
19. The half-life of 231Pa is 3.25 x 104 years. How much of an initial 10.40 microgram sample remains after 3.25 x 10 years? (a) 0.0120 micrograms (b) 0.240 micrograms (c) 2.18 micrograms (d) 0.0102 micrograms (e) 1.04 micrograms
(25 pts) The half-life for the process 238U ---...--> 206Pb is 4.5 x 109 yr. A mineral sample contains 85.0 mg of 238U and 10.0 mg of 206Pb. (a) What is the age of the sample? (b) What is the 238U activity in Bq (becquerel) of the original mineral sample ?
Sr-90 has a half-life of 29.1 years. How long will it take for the activity of a Sr-90 sample to decay from 5.3 times 10^3 dpm (disintegrations per minute) to 3 times 10^2 dpm? The half-life of a radioisotope is 3 d. What percent remains after 1 week?
(Show the work for these questions) 35. What is the half-life of a medication for which only 12.5% remains after 24 hours? A. 4 hours B. 8 hours C. 16 hours D. None of the above 36. What is the half-life of an orally administered medicated syrup if its level is down to 61⁄4 % after 12 hours? A. 6 hours B. 4 hours C. 3 hours D. 2 hours 37. When a 500-mg medical dosage has degenerated to approximately...
The half-life of a certain radioactive element is about 1000 years. After 3500 years, what percentage P of a sample of this element remains ? About % of the sample remains. (Round to the nearest tenth as needed.)
5.3.131 The half-life of a certain radioactive element is about 1600 years. After 2900 years, what percentage P of a sample of this element remains? About % of the sample remains (Round to the nearest tenth as needed.)
h= half life a0 = original amount a(t) = amount present after t years t = time What information do you need? TH 100 - D100 Use equation : acca un Page 4 of 5 4. Suppose we have Xo amount of a certain radioactive substance. It has been observed that this substance losses 5% of its mass every 10 years. @ How much of the initial mass Xo remains after 10 years? What about 20 years? (b) Use the...
4. The radioactive isotope 55Fe has a half-life of 2.73 years. (a) What is the rate constant for this first-order reaction? (b)What fraction of the isotope remains after 1 years? Assume 3 significant figures in your calculations