1 g of an α-emitting nuclide _ZX^A (t_1/2 = 10 h) was placed in a sealed container. The time require — Nuclear Chemistry and Radioactivity Chemistry Question

💡 Solution & Explanation

1. Moles of Helium atoms accumulated = 4.52 * 10^23 / 6.022 * 10^23 = 0.75 mol.<br>2. Since each α decay produces exactly one helium atom, the moles of active nuclide decayed is 0.75 mol.<br>3. In '1 g' (which stands for 1 g-atom, i.e., 1.0 mole of initial atoms), the fraction decayed is 0.75 / 1.0 = 0.75, which means the fraction remaining is 1.0 - 0.75 = 0.25 (or 1/4 = (1/2)^2).<br>4. This corresponds to exactly 2 half-lives: t = 2 * t_1/2 = 2 * 10 h = 20.0 h.