Question

10 g of a radioactive isotope is reduced to 1.25 s in 12 yr. Therefore, half-life period of the isotope is

• A. 3yr
• B. 4yr
• C. 8yr
• D. 24yr

Answer 1

Answer: (B)

$[R]=\frac{{[R]}_0}{2^n}$ $\therefore$ $1.25=\frac{10}{2^n}$ or $2^n=\frac{10}{1.25}=8=2^3$ Hence, $n=3$ 3 half-lives $=12yr$ or $t_{1/2}=4yr$