A radionuclide 'A' decays simultaneously into 'B' and 'C', by - and -emission, respectively. The hal — Nuclear Chemistry and Radioactivity Chemistry Question

💡 Solution & Explanation

Effective decay constant $\lambda = \lambda_1 + \lambda_2 \implies \frac{1}{t_{eff}} = \frac{1}{20} + \frac{1}{60} = \frac{4}{60}$. Thus $t_{eff} = 15 \text{ min}$. 87.5% decay means 12.5% (which is 1/8) remains. This takes 3 half-lives. Time = $3 \times 15 = 45 \text{ min}$. Therefore, correct answer is C.