# Chemistry

Which radioactive sample would contain the greatest remaining mass of the radioactive isotope after 10 years?
A. 2.0 grams of 198 Au
B. 2.0 grams of 42 K
C. 4.0 grams of 32 P
D. 4.0 grams of 60 Co

By the way the numbers next to the elements are their atomic masses. thanks again

You must look up the half-life of each of the isotopes. Surely you have a text or notes that will furnish this. Co-60 is the only one I know from memory for I worked with it many years ago. It is 5.1 years half-life. Then half of the mass will remain after 1 half life, 1/4 will remain after two half lives, etc.
You can also use
ln(No/N)=kt I can help with that if you need help after you obtain the half lives.

1. 👍 2
2. 👎 0
3. 👁 2,469
1. Hd

1. 👍 0
2. 👎 1
2. It is D
4.0 grams of 60Co

1. 👍 4
2. 👎 0
3. It is choice (D)
4.0 grams of 60Co

1. 👍 2
2. 👎 0

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