Question 1

Based on the provided decay curve, what is the approximate half-life of the radioisotope shown in the graph?

Accepted Answer

About 4 days

Question 2

If you start with 100 mg of this radioisotope, approximately how much would remain after 12 days according to the graph?

Accepted Answer

About 6.25 mg

Question 3

Which equation best describes the fraction of radioisotope remaining after $$n$$ half-lives?

Accepted Answer

$$\left( \frac{1}{2} \right)^n$$

Question 4

If the initial sample contains 80 mg of the isotope, how much would remain after 3 half-lives?

Accepted Answer

20 mg

Question 5

A scientist measures 12.5% of the original isotope remaining. How many half-lives have passed?

Accepted Answer

4

Question 6

If the half-life is 4 days, what percentage of the isotope remains after 16 days?

Accepted Answer

6.25%

Question 7

Which of the following statements is correct regarding the decay curve shown?

Accepted Answer

The isotope decays by half its amount every half-life.

Question 8

If a patient is given a dose of 100 mg of this isotope, how much would remain after 8 days?

Accepted Answer

12.5 mg

Question 9

Which mathematical expression would you use to calculate the remaining mass $$m$$ after time $$t$$, given the half-life $$t_{1/2}$$ and initial mass $$m_0$$?

Accepted Answer

$$m = m_0$ \left( \frac{1}{2} \$$right)^{\frac{t}$${t_{1/2}}}$$

Question 10

If the isotope's half-life is 4 days, how many days will it take for the sample to decay to less than 1% of its original amount?

Accepted Answer

20 days

Ch. 4 Nuclear Chemistry: Radioactivity, Nuclear Reactions, and Measurement

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