How long will it take for a quarter of the uranium 238 atoms in a rock to decay to lead 206?
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How long will it take for a quarter of the uranium 238 atoms in a rock to decay to lead 206?
about 4.5 billion years
Radiometric Dating Some examples: the half-life for the decay of potassium 40 atoms into argon 40 atoms is about 1.3 billion years, the half-life for the decay of uranium 238 into lead 206 is about 4.5 billion years, and the half-life for the decay of carbon 14 into Nitrogen 14 is 5730 years.
What is the age of rock if it contains uranium 238?
The half – life of U 238 is about 4.5 billion years.
What of U 238 will remain after three half-lives?
13.5 billion years
Explanation: The mass of Uranium halves every 4.5 billion years, so 13.5 billion years= 3 half-lives.
How was the half-life of uranium 238 determined?
The half-life is then determined from the fundamental definition of activity as the product of the radionuclide decay constant, λ, and the number of radioactive atoms present, N. A = 1014 cpm/0.315 c d-1 = 3219 dpm = λ N = (ln2/T1/2)(4.41 x 10-3 g/238.03 g/g-atomic weight)(6.022 x 1023 atoms/g-atomic weight).
How old would a sample with 50\% uranium-238 and 50\% lead-206 be?
After a second half-life, the 50 gm of U-238 would drop to 25 while the 50 gm of Pb-206 would increase to 75. Thus, two half lives. Since the half-life of U-238 is 4.5 Billion years, this rock must be 9 BY old. 1d.
How is the half-life of a radioactive isotope determined?
One important measure of the rate at which a radioactive substance decays is called half-life, or t1/2. Half-life is the amount of time needed for one half of a given quantity of a substance to decay. By measuring the decay of a sample of barium-137, you will be able to calculate its half-life.
What is the half-life of uranium-238 quizlet?
Uranium-238 has a half-life of 4.5 billion years.
How old is a rock sample that contains uranium-235 and lead-207 in equal amounts?
704 million years
RADIOMETRIC TIME SCALE
| Parent Isotope | Stable Daughter Product | Currently Accepted Half-Life Values |
|---|---|---|
| Uranium-238 | Lead-206 | 4.5 billion years |
| Uranium-235 | Lead-207 | 704 million years |
| Thorium-232 | Lead-208 | 14.0 billion years |
| Rubidium-87 | Strontium-87 | 48.8 billion years |