Question

Weight of ${}^{14}C$ to have radioactivity 1 curie [$\lambda$ (disintegration constant) $=4.4\times {10}^{-12}{S}^{-1}$] is :

• A. $8\times {10}^{-4}$ kg
• B. $2\times {10}^{-4}$ kg
• C. $25\times {10}^{-4}$ kg
• D. $2\times {10}^{-3}$ kg

Answer 1

Answer: (B)

$2\times {10}^{-4}$ kg

As we know,

$-\frac{dN}{dt}=kN=k\frac{w}{A}{N}_0$

$3.7\times {10}^{10}=4.4\times {10}^{-12}\times \frac{w}{14}\times 6.02\times {10}^{23}$

$w=2\times {10}^{-4}$ kg $(1Ci=3.7\times {10}^{10}dps)$