question 1-2\na sample of radium has a weight of 12.8 mg and a half-life of approximately 6 years.\nhow much…

question 1-2\na sample of radium has a weight of 12.8 mg and a half-life of approximately 6 years.\nhow much of the sample will remain after 18 years?\nselect the best answer.\n○ 1.4 mg\n○ 1.6 mg\n○ 3.2 mg\n○ 6.4 mg

question 1-2\na sample of radium has a weight of 12.8 mg and a half-life of approximately 6 years.\nhow much of the sample will remain after 18 years?\nselect the best answer.\n○ 1.4 mg\n○ 1.6 mg\n○ 3.2 mg\n○ 6.4 mg

Answer

Explanation:

Step1: Calculate number of half-lives

$\text{Number of half-lives} = \frac{18}{6} = 3$

Step2: Calculate remaining mass

$\text{Remaining mass} = 12.8 \times \left(\frac{1}{2}\right)^3 = 12.8 \times \frac{1}{8}$

Answer:

C. 1.6 mg