November 28, 2015

Homework Help: Chemistry *URGENT*

Posted by Anon on Friday, March 5, 2010 at 4:49am.

URGENT help!

3. A rock sample was dated using potassium-40, Neasyrenebt ubducated tgat 1/8 of the original parent isotope is left in the rock sample. How old is the rock?

5. When a sample of lava solidfied, it contained 28g of uranium-238. It that lava sample was later found to contain only 7g of uranium-238, how many years had passed since the lava solidified?

6. AFter 25 years, the number of radioactive cobalt atoms in a sample is reduced to 1/32 of the original count. What is the half-life of this isotope?

How would you find the answers to these questions?
TEll me the steps.

Thank you very much.

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