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March 4, 2015

March 4, 2015

Posted by **Anonymous** on Wednesday, April 16, 2014 at 12:53am.

A radioactive isotope source has a mass of 120 g. If the isotope has a half life of 20 secs what would be the mass of the isotope in 2 mins?

- Radioactivity -
**DrBob222**, Wednesday, April 16, 2014 at 1:12amk = 0.693/t

_{1/2}

Substitute k into the equation below.

ln(No/N) = kt

No = 120

N = ?

k from above

t = 120 seconds (since the half life is given in sec you will have a seconds terms for k so you must convert 2 minutes to seconds).

Solve for N.

See the link below for the definition of Bq.

http://en.wikipedia.org/wiki/Becquerel

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