Question

This chart show the amount of radioactivity measured from three unknown isotopes. Which statement describes each of the isotopes? Isotope A was measured at day 24, Isotope B was measured at day 6, and Isotope C was measured at day 10. Isotope A was measured at day 18, Isotope B was measured at day 4, and Isotope C was measured at day 5. Isotope A was measured at day 24, Isotope B was measured at day 8, and Isotope C was measured at day 20. Isotope A was measured at day 30, Isotope B was measured at day 6, and Isotope C was measured at day 10.

Answer 1

Answer: Isotope A was measured at day 24, Isotope B was measured at day 6, and Isotope C was measured at day 10.

Explanation:

The half-life time is defined as the time needed for the radioactive isotope to decay to the half of its initial concentration.

• Isotope A: its starting weight 95 g and its ending measured weight is 5.9.

95 → 47.5 (half-life 1) → 23.75 (half-life 2) → 11.875 (half-life 3) → 5.9 (half-life 4).

It needs 4 half-lives to decay from 95 to 5.9.

half-life time of isotope A = 6 days.

the time taken to measure isotope A = (4 x 6 days) = 24 days.

• Isotope B: its starting weight 20 g and its ending measured weight is 2.5.

20 → 10 (half-life 1) → 5 (half-life 2) → 2.5 (half-life 3).

It needs 3 half-lives to decay from 20 to 2.5.

half-life time of isotope B = 2 days.

the time taken to measure isotope B = (3 x 2 days) = 6 days.

• Isotope C: its starting weight 45 g and its ending measured weight is 22.5.

45 → 22.5 (half-life 1)

It needs 1 half-life to decay from 45 to 22.5.

half-life time of isotope C = 10 days.

the time taken to measure isotope C = (1 x 10 days) = 10 days.

Answer 2

Answer:

the answer is A

Explanation: