Question

Ba-122 has half life of $2$ minutes. An experiment has to be done using Ba-122 and it takes $10$ minutes to set up the experiment if initially $80 \,gm$ of $Ba -122$ was taken how much $Ba -122$ was left when experiment was started?

• A. 2.5 gm
• B. 5 gm
• C. 10 gm
• D. 20 gm

Answer 1

Answer: (A)

Given, half life $t_{1 / 2}=2 min$
Total time, $T =10 min$
No. of half life, $n =\frac{10}{-2}=5$
Then remaining Ba-122 is given by, $\Rightarrow \frac{N_{0}}{2^{n}}=\frac{80}{2^{5}}=\frac{80}{32}=2.5$