Question 1
A nuclide has a decay constant of 4.28 × 10
-4/h. If the activity of a sample is 3.14 × 10
5/s, how many atoms of the nuclide are present in the sample?
◦ 7.34 × 10
8 ◦ 2.64 × 10
12 ◦ 4.84 × 10
5 ◦ 1.34 × 10
2 ◦ 2.34 × 10
11 Question 2
A rock contains 0.313 mg of lead-206 for each milligram of uranium-238. The

for the decay of uranium-238 to lead-206 is 4.5 × 10
9 y. The rock was formed ________ y. ago.
◦ 1.41 × 10
9◦ 1.08 × 10
9◦ 1.39 × 10
9◦ 2.00 × 10
9◦ 1.56 × 10
9