Question

What are the half lives for uranium-235 and uranium-238?

a.
The half-life of uranium-235 is 713 seconds, the half-life of uranium-238 is 4.5 minutes
c.
The half-life of uranium-235 is 713,000,000 years, the half-life of uranium-238 is 4,500,000,000 years
b.
The half-life of uranium-235 is 713 days, the half-life of uranium-238 is 450 days
d.
None of the above

Answer 1

The half-life of uranium-235 is 703 million years, while the half-life of uranium-238 is 4.5 billion years. Option c is the correct answer, with the half-lives being in years, not seconds or days.

Step-by-step explanation:

The correct half-lives for the uranium isotopes are as follows: uranium-235 (U-235) has a half-life of 703 million years (703,000,000 years), and uranium-238 (U-238) has a half-life of 4.5 billion years (4,500,000,000 years). Therefore, the right answer is option c: The half-life of uranium-235 is 713,000,000 years, the half-life of uranium-238 is 4,500,000,000 years. As for the question about the percentage of U-238 that has decayed over the lifetime of the universe, which is estimated at 13.8 billion years, we would expect a significant portion to have decayed due to its long half-life.

Answer 2

C. The half-life of uranium-235 is 713,000,000 years, the half-life of uranium-238 is 4,500,000,000 years