After 4.00 years a 2.0 g sample of a radioisotope remains from a sample that had an original mass of 4.00 g. Calculate the half life of this mysterious substance. How much of the radioisotope remains after 20 years?

How many half-lives did a radio-active sample complete is 2.5 g of a sample remains from 20.0 g initial material?

24g of an unknown radioactive substance decays to 1.5g after 180 seconds. What is the half-life of this substance?

4. The half-life of radioactive radium-224 is 3.50 days. What was the original mass if 0.200 g remains after 10.50 days? A. 0.025 g B. 0.050 g C. 1.60 g D. 0.60 g

QUESTION 7 Supposed that a radioactive substance has decayed until only of 1/8 of it remains. For how many half-lives has it been decaying? 4 in

A wooden artifact from an ancient tomb contains 30 percent of the carbon -14 that is present in living trees. How long ago, to the nearest year, was the artifact made?( The half-life of carbon-14 is 5730)

A wood carving is found in the excavation of an abandoned settlement. A sample from this carving is found to have a C-14 content that is 25.0% of that of living trees. How old is the object? The half-life of carbon 14 is 5730 years.

A volcanic eruption melts a large chunk of rock, and all gases are expelled. After cooling, argon-40 accumulates from the ongoing decay of potassium-40 (half-life of potassium-40 is 1.25 x 109 yr) in the rock. When a piece of rock is analyzed, it is found to contain 1.38 mmol of potassium-40 and 1.14 mmol of argon-40. How long ago did the rock cool?

The Cs-131 nuclide has a half-life of 30 years. After 120 years, 2.5 g remain. What is the original mass of the Cs-131 sample in grams?