Half-life Knowledge-Based Download PDF

Questions

1. 1.

   Assuming a closed rock sample initially contained no daughter isotope, what is the ratio of stable daughter nuclei to radioactive parent nuclei after four half-lives have elapsed?

   • A) 15 : 1
   • B) 16 : 1
   • C) 7 : 1
   • D) 4 : 1
2. 2.

   After a period of 56.0 days, a radioactive sample with a half-life of 14.0 days contains 1.50 mg of the original radioisotope. What was the initial mass of the radioisotope in the sample?

   • A) 24.0 mg
   • B) 12.0 mg
   • C) 6.00 mg
   • D) 0.0938 mg
3. 3.

   A radioactive nuclide has a half-life of 4.5 hours. How much time must elapse for 93.75% of the original radioactive nuclei in a sample to decay?

   • A) 9.0 hours
   • B) 12.0 hours
   • C) 13.5 hours
   • D) 18.0 hours
4. 4.

   A radioactive sample initially exhibits an activity of 800 Bq. If its activity decreases to 100 Bq after 15 hours, what is the half-life of this radioisotope?

   • A) 2.5 hours
   • B) 3.0 hours
   • C) 3.75 hours
   • D) 5.0 hours
5. 5.

   A sample initially contains 64.0 mg of iodine-131, which has a half-life of 8.0 days. What mass of iodine-131 remains after 32.0 days?

   • A) 8.0 mg
   • B) 4.0 mg
   • C) 2.0 mg
   • D) 16.0 mg