6. A rock contains 0.257 mg of lead-206 for every milligram of uranium-238. The half-life for the decay of uranium-238 to lead-206 is 4.5 x 10° years. How old is the rock?

Radioactive vanadium-48 decays with a half-life of 16.0 days. a. What is the value of k in s? k = b. A sample contains 84.0 mg *°V. How many decay events will be produced in the first second? Assume the atomic mass of **V is 48.0 u. decays/s c. A chemist obtains a fresh sample of 48 V and measures its radioactivity. She then determines that to do an experiment, the radioactivity cannot fall below 25% of the initial measured value. How long does she have to do the experiment? days

The currently accepted value for the half-life of radiocarbon is 5,730 years. Based on that information, which of the following conclusions is correct. 1. In 2,865 years, the entire original amount of carbon-14 in the sample will be gone. 2. In 11,460 years, the entire sample will be another element. 3. In 5,730 years, half of the original sample of carbon will be gone. 4. In 5,730 years, half of the original amount of carbon-14 in the sample will be gone.

2. Iodine-131 is used medically for the diagnosis of thyroid illnesses. The rate constant for the decay of I-131 was found to be 8.66 x 10/day. a. Calculate the half-life of I-131. b. If 0.25 mg of I-131 was administered to a patient, how much of the isotope (in g) will remain after 120 hours?

What is the half-life of uranium-238 if 9.10×109 years are required for the activity of a sample of uranium-238 to fall to 24.7 percent of its original value?

The half-life o carbon-11 is 20.3 min. How long will it take for 69% of a sample to decay? How long will it take for 90% of a sample to decay?

The half-life of Strontium-85 is 65 days. How much of a 80. mg sample is left after 260 days? mg