Chemistry

posted by .

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?

  • Chemistry -

    mass U-238 originally is mass Pb x (238/206) = 16.0 x (206/238) = about 13.8 but you need to get a more accurate answer.
    mass U-238 initially = 66 mg + 13.8 = about 80.
    k = 0.693/t1/2 - 0.693/4.5E9 = 1.5E-10(approx)

    Substitute these values into the first order equation below and solve for t (in years).
    ln(No/N) = kt
    No = about 80
    N = 66
    k from above.
    t = unknown.

    All of the numbers above are estimates. You should go through and confirm everything.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Earth Science

    can someone help me? you are given a sample of an unknown mineral. you determine that the mineral's streak is whte and its specific gravity is 2.8. is the mineral most likely to be a metallic mineral or a nonmetallic mineral?
  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. Half-Life

    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?
  5. 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 …
  6. chemistry help!!

    The half-life for the process 238U 206Pb is 4.5 109 yr. A mineral sample contains 45.9 mg of 238U and 16.8 mg of 206Pb. What is the age of the mineral?
  7. Chemistry

    This question has been bugging me for a long time. A rock contains a Pb-206 to U-238 mass ratio of .145 to 1.00. Assuming that it did not contain any Pb-206 at the beginning of its formation, determine its age. I assume from the other …
  8. Chemistry

    Pu-238 is radioactive by alpha-decay (half-life 87.7 y). Each decay releases 5.6 MeV of energy. Pu-238 is sometimes used to power space probes. If all the decay energy can be converted to electric power, what mass of Pu-238 would be …
  9. college gen chem

    An igneous rock contains a Pb−206/U−238 mass ratio of 0.367. How old is the rock?
  10. Chemistry

    A rock contains 270 mmol of 238 U (t1/2= 4.5*10^9 yr) and 110 mmol of 206 Pb. Assuming that all the 206 Pb comes from decay of the 238 U, estimate the rock’s age.

More Similar Questions