[dylancampbell]

I have some questions I can't figure out that relate to Nuclear Chemistry:

1) A radioactive nuclide of mass number 94 has been prepared by neutron bombardment. If 4.7 mg of this nuclide register 20 counts per minute on a radioactivity counter, what is the half-life of this nuclide? (Enter in years.)

What confuses me about this one is what exactly it means by "counts per minute" on a radioactivity counter. I need some way to convert that into Curies, or some other unit I know.

2) Uranium-238 undergoes eight consecutive alpha-emissions to give stable lead. In an uranium ore sample, all the alpha-particles are quickly stopped, becoming trapped 4He atoms. If analysis of a rock sample shows it to contain 7.86x 10^-5 cm3 of helium (1~atm, 298~K) and 1.20x 10^-7g 238U per gram of rock, what is the estimated age of the rock? The half-life of uranium-238 is 4.51x10^9 years. (Express your answer in years.)

This one I am just confused about in general. Any help would be greatly appreciated.