75% of a quantity of U-232 remains after 30 years. What is the half-life?

The remains of an ancient cave were unearthed. Analysis from charcoal in the  cave gave 12.0 disintegration/min/g of carbon. The half life of C-14 is 5730 years. Analysis of the tree cut down when the cave was unearth showed 22.1 disintegrations/min/g of carbon. How old are the remains in the cave?

The activity of C-14 can be used to determine the age of some archaeological discoveries. Suppose a sample of ancient wood which contains C-14 has an activity of 7.50 x 10^-4 Ci. The half life of C-14 is 5730 years. What will be the activity of this sample after 250 years?

After 1.80 days, the activity of a sample of an unknown type radioactive material has decreased to 80.4% of the initial activity. What is the half-life of this material?

Archeologist extracted 179 gm of carbon from an animal bone from an archeological site. The carbon shows an activity of 15 decays/s. (Half-life of 146C = 5730 years, 1 year = 3.156 x 107 seconds, Avogadro's number = 6.02 x 1023 atoms/mol) (A) Total number of atoms in this carbon sample =        . (B) Decay constant of 146C, λ =           . (C) Number of 146C atoms in this sample =          . (D) Activity of 146C at time (t = 0) =            . (E) Age of the animal =

Question 3. Two nuclei having the same mass number are known as isobars. (a)Calculate the difference in binding energy per nucleon for the following two isobars Na and Mg. (b) How do you account for this difference? (The mass of ?3Mg = 22.994 127 u.) 23

9. A rock that contains 1.2x10-12 mol of 232Th (t1/2 = 1.4x1010 yr) has 4.2x105 fission tracks, each track representing the fission of one atom of 232Th. How old is the rock?

What is the half -life of potassium-40 if 1.70×10^19 nuclei have an activity of 300 Bq

You inherit 32 kg of cesium-136 after your roommate moves out and leaves it behind. Cesium-137 has a half-life of 30 years. If you pack it in a box and forget about it, but your grandchildren finds it in the attic 90 years from now, how much of the sample is still cesium-137?

Two nuclei having the same mass number are called isobars. Calculate the difference in binding energy per nucleon for the isobars 2311Na and 2312Mg. How do you account for the difference?