A 53.8-mg sample of sodium perchlorate contains radioactive chlorine-36 (whose atomic mass is 36.0 amu). If 29.6% of the chlorine atoms in the sample are chlorine-36 and the remainder are naturally occurring nonradioactive chlorine atoms, how many disintegrations per second are produced by this sample? The half-life of chlorine-36 is 3.0 × 105yr.
I am trying to find the correct number of radioactive Cl nuclei, but am uncertain if the procedure I used is correct.
n=m/M=(53.8mg/(1000g/mg))/122.44g/mol
=4.39398889...x10^-4mol
At this point, I am not whether this molar quantity of NaClO4 is equivalent to that Cl overall or if I am supposed to take the fraction of the molecule that is Cl and multiply by the calculated molar value (which would be 1/6). once I have clarified this I should be fine.
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I don't think the molar mass of the 58.3 mg sample is 122.44 nor do I think you can calculate what it is. The NaClO4 contains Cl35, Cl36, Cl37in this sample. You know the percent Cl36 but you don't know the percentages of the other two (except of course in naturally occurring NaClO4.) So I think you must start with 58.3 mg NaClO4 x 0.296 = ?mg Cl-36 and you convert that to atoms of Cl-36. Knowing atoms you can go to dps.
1 answer