A) 125 mg
B) 62.5 mg
C) Nothing will be left
D) 31.25 mg
Correct Answer: B
Solution :
Given, \[{{T}_{1/2}}=5.25\,yr\] \[t=21\,yr\] Number of half lives \[n=\frac{t}{{{T}_{1/2}}}=\frac{21}{5.25}=4\] Amount of sample left \[={{\left( \frac{1}{2} \right)}^{4}}\times 1\,g\] \[=\frac{1}{16}g\]or\[62.5mg\]
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