Question

The half life of $P{a}^{218}$ is 3 minutes. What fraction of 10g sample of $P{a}^{218}$ will remain after 15 minutes ?

• A. $\frac{1}{5}$
• B. $\frac{1}{25}$
• C. $\frac{1}{32}$
• D. $\frac{1}{64}$

Answer 1

Answer: (C)

$\frac{N}{N_0}={\left(\frac{1}{2}\right)}^{t/T}={\left(\frac{1}{2}\right)}^{15/3}={\left(\frac{1}{2}\right)}^5=\frac{1}{32}$