Half-Life

posted by .

Uranium-238 decays to Lead-206. The half life of Uranium-238 is 4.5 billion years. If you have a 100 g sample. How much sample will you have after 2 half lifes?

  • Half-Life -

    just do it in your head ...

    after 1 half-life you would have 50 g left
    after 2 half-lifes you would have 25 g left

  • Half-Life -

    Your question isn't quite clear to me. If you want the mass of U after two half lives, then 25 g is correct. If you want the mass of sample left after two half lives, that is 25g U + the equivalent of 75 g U that's been converted to Pb. That conversion is 75 g U x (atomic mass Pb/atomic mass U) = about 75*207/238 = about 65 g. Therefore, the total mass is 25 + about 65 = about 90 g.

  • Half-Life -

    If the half-life of a radionuclide is 1 month, is a sample of it completely decayed after 2 months?

  • Half-Life -

    4.5 ×1o ^ 9

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry *URGENT*

    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?
  2. geology

    How old are the oldest meteorites yet studied and what is the minimum age of Earth since Earth is at least as old as the meteorites. We know the oldest meteorites contain equal amounts of uranium 238 and lead 206. Uranium 238 has a …
  3. Chem 2

    The half-life for the radioactive decay of U-238 is 4.5 billion years and is independent of initial concentration. a) How long will it take for 10% of the U-238 atoms in a sample of U- 238 to decay?
  4. algebra

    The half-life of 234U, uranium-234, is 2.52 105 yr. If 97.7% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?
  5. Chemistry

    The half-life for the process 238 U --> 206 Pb is 4.5*10^9 yr. A mineral sample contains 66.0 mg of 238 U and 16.0 mg of 206Pb. What is the age of the mineral?
  6. Chemistry

    Uranium-238 has half life of 4.51 * 10^9 years Uranium-234 has half life of 2.48 * 10^5 years Thorium-230 has half life of 8.0 * 10^4 years Radium-226 has half life of 1.62 * 10^3 years Lead-210 has half life of 20.4 years. The rate …
  7. Chemistry 1046

    Geologists can estimate the age of rocks by their uranium-238 content. The uranium is incorporated in the rock as it hardens and then decays with first-order kinetics and a half-life of 4.5 billion years. A rock contains 65.7% of the …
  8. Chemistry

    Geologists can estimate the age of rocks by their uranium-238 content. The uranium is incorporated in the rock as it hardens and then decays with first-order kinetics and a half-life of 4.5 billion years. A rock is found to contain …
  9. Science

    Starting with 100 grams of uranium-238, after one half life has gone by, how many grams of uranium-238 will remain?
  10. Earth Science

    1. We start with 400 atoms of Uranium-238. How many remain after 4.5 billion years?

More Similar Questions