A radioactive isotope has a half-life of 74.0 min . A sample is prepared that ha

Question

A radioactive isotope has a half-life of 74.0 min . A sample is prepared that has an initial activity of 1.30×1011 Bq .

Part A

How many radioactive nuclei are initially present in the sample?

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Part B

How many are present after 74.0 min ?

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Part C

What is the activity after 74.0 min ?

A radioactive isotope has a half-life of 74.0 min . A sample is prepared that has an initial activity of 1.30×1011 Bq .

Part A

How many radioactive nuclei are initially present in the sample?

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Part B

How many are present after 74.0 min ?

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Part C

What is the activity after 74.0 min ?

Explanation / Answer

Part A)      Here,   time constant tc = thalf/ln(2) = 74//ln(2)    =   106.759   min

radioactive nuclei are initially present in the sample =   106.759 * 60 * 1.30×1011

                                                                                                                      =   8.327 * 1014

Part B)    present after 74.0 min   =   106.759 * 60 * 1.30×1011 /2

                                                      = 4.1635 * 1014

Part C)     activity after 74.0 min   =   1.30×1011/2

                                                       =    6.5 * 1010   Bq

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