Asked by Trixie
                A sample of pure cobalt-60 has an activity of 8 µCi.
(t1/2 cobalt-60 = 5.26 a)
(a) How many atoms of cobalt-60 are present in the sample?
atoms
(b) What is the mass in grams of the sample?
g
The way I approached part a was to first convert the microCi into Bq (for a value of 296000 Bq). I then tried to find the decay constant, k, by converting 5.26a into seconds (for a value of 16.6E7 s) and using the equation ln2/((16.6E7) and ended up with 4.17E-9 (note: for the t I used more significant values then listed)....
After this I'm not so sure...but I tried using N=-dN/dT= (-2960000/(4.178E-9)= -7.083E12 atoms...which is of course wrong. Can someone redirect me in my way of thinking?
Thanks
            
        (t1/2 cobalt-60 = 5.26 a)
(a) How many atoms of cobalt-60 are present in the sample?
atoms
(b) What is the mass in grams of the sample?
g
The way I approached part a was to first convert the microCi into Bq (for a value of 296000 Bq). I then tried to find the decay constant, k, by converting 5.26a into seconds (for a value of 16.6E7 s) and using the equation ln2/((16.6E7) and ended up with 4.17E-9 (note: for the t I used more significant values then listed)....
After this I'm not so sure...but I tried using N=-dN/dT= (-2960000/(4.178E-9)= -7.083E12 atoms...which is of course wrong. Can someone redirect me in my way of thinking?
Thanks
Answers
                    Answered by
            DrBob222
            
    I think your next step is Ro=kNo
The activity, Ro, = 296,000 dps
k = 4.178 x 10^-9 sec^-1, solve for No. Check my thinking.
    
The activity, Ro, = 296,000 dps
k = 4.178 x 10^-9 sec^-1, solve for No. Check my thinking.
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