Need help with these questions, thank you! Constants and Conversion Factors 6.02

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Need help with these questions, thank you!

Constants and Conversion Factors 6.023 x 102mol Number of atoms per moleAvogadro's number, A Number of grams of C per mol. 137g mol 1 1) If a sample has 3 x 105 decays in 4 seconds, what is the activity in Ci? Cíl submit 2) How many atoms of 131I are in a sample with activity of 2 mCi given that the half-life of 131I is 8.023 days? toms Submit 3) 137Cs, is a radioisotope that is often used for the calibration of radiation detectors, such as those used in PET scanners. If you have 2 x 1012 atoms of 137Cs, what will the activity be after 50 years assuming that the half-life of 137 Cs is 30.07 years? Bq Submit 4) In a real world situation, we would measure the quantity of a substance in grams rather than atoms. What if, instead of 2 x 1012 atoms, you started with 1 gram of 137 Cs? Bq Submit Help

Explanation / Answer

Activity = dN/dt

Plugging values,

Activity = (3*10^5)/(4)= 7.5*10^3 Bq

1 Ci= 3.7*10^10 Bq

1 Bq = 2.7*10^-11 Ci

Thus,

Activity = 7.5*10^3 Bq = (7.5*10^3)*(2.7*10^-11) = 2.025*10^-7 Ci

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