Main Menu Contents Gradesl |Syllabus Timer Notes Evaluat eedback2 Course T0 The

Question

Main Menu Contents Gradesl |Syllabus Timer Notes Evaluat eedback2 Course T0 The activity of a radioactive sample is initially 1014 decays per second and it decreases to 1010 decays per second after 30 days. Find T and t1/2 of this radioactive element in hours. Also the initial number of radioactive nuclei in the sample. ? 130 Solve for T ir the decay equation R-Ro exp[-t/ hours Submit Answer Incorrect. Tries 1/3 Previous Tries nuclei Submit Answer Incorrect. Tries 1/3 Previous Tries Threaded View Chronological View Othsr Export NEW Part 2 Question Mazin G. Nasir Reply (Mon Apr 23 10:57:13 am 2018 (EDT)) My general preferences on what is marked as NEW Mark NEW posts no longer new How can the decay rate be converted to number of nucleons? We'd need either N at a certain time to find N 0 or even if we can set N to zero to find N.O, In(O)

Explanation / Answer

A = A0 e^(- t / T )

10^10 = 10^14 e^(-30/T)

T = 3.257 day

T = 78.2 hrs ....Ans

and ln(2) / half life = 1 / T

half life (t1/2) = T ln(2)

= 54.2 hrs .....Ans

A0 = lambda N0

and lambda = ln(2) / half life

= 0.0128 hr^-1

= 3.553 x 10^-6 s^-1

so N0 = (10^14)/(3.553 x 10^-6)

N0 = 2.81 x 10^19 nuclei ....Ans

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