Question

16. What will he the level of activity (in terms of X) after two half lives have elapsed?

17. What would the activity of a the above sample be if we tripled its size?

18. If the initial activity of 0.365 grams of the above sample is Y Bq, what would the activity be if we increased the initial sample to 0.950 grams?

The decay curve of a radioactive nuclide 1000 sample is shown. Its initial activity is measured to be X Bq. 14, what is the population at t = 8.0 hours? 14. 15. After how many half lives will the 00 population be 125 nuclides? 3 15. 16. What will be the level of activity (in terms of X) after two half lives have elapsed? 0.0 8.0 16 24 t/hours 16.

Answer 1

Based upon concept of half life, decay constant and activity

Based upon concept of half life, decay constant and activity \r\n Initial activity = X Bq From decay curve, it is clear that half life T_1/2 = 5 hrs 14. From graph, population at t = 8.0 hrs is 320 15. N/N_0 = 125/1000 = 1/8 = (1/2)^4 therefore Time is equal to 4 half lives. 16. Level of activity after 2 half lives = X/4 Bq 17. Activity R = lambda N_0 where lambda = decay constant & N_0 is initial population, so if N_0 is tripled, activity will also be tripled. Therefore X prime = 3X Bq 18. Y prime/y = N prime/N doublerightarrow y prime/y = 0.950/0.365 = 3.6 therefore y prime = 2.6 y Bq