Approximately how many radioactive atoms are present in a tritium sample with an activity of 0.20 × 10−⁶ Ci and a half-life of 12.3 years? (1 Ci = 3.7 × 10¹⁰ decays/s) A)1.3E+5 B)1.1E+2 C)3.5E-6 D)4.1E+12 E)2.9E+12

Question

Quizplus · Accepted Answer

We can use the following equation to relate activity (A) and number of radioactive atoms (N) of a sample:
A = λN, where λ is the decay constant.

We can also use the fact that the half-life (t1/2) is related to the decay constant by:

t1/2 = ln(2)/λ

Rearranging the first equation, we get:

N = A/λ

Substituting the value of λ from the second equation, we get:

N = A t1/2 / ln(2)

Substituting the given values, we get:

N = (0.20 × 10^0 Ci) × (12.3 years) / ln(2) × (3.7 × 10^10 decays/s)

N = 4.1 × 10^12

Therefore, the answer is D) 4.1E+12.

Approximately How Many Radioactive Atoms Are Present in a Tritium