Magnesium, studied as a biodegradable metal, corrodes in body fluids as Mg + 2H₂O → Mg(OH)₂ + H₂. When a 0.10 g magnesium screw corrodes completely, which value is closest to the volume of hydrogen released? Take the molar mass of Mg as 24.31 g/mol and the molar volume of gas at 37℃ and 1 atm as 25.4 L/mol.

Answer: B. About 104 mL

The amount of Mg is 0.10/24.31 ≈ 4.11×10⁻³ mol. Mg gives up 2 electrons when it becomes Mg²⁺, and those electrons turn 2 H⁺ into 1 H₂ molecule, so 1 mol of H₂ is released per mol of Mg. The volume is 4.11×10⁻³ × 25.4 L ≈ 0.104 L, about 104 mL. Even a single screw releases this much gas, so fast corrosion causes the problem of gas accumulating in tissue, and research is under way to slow the corrosion to match bone healing by alloying and surface treatment. About 52 mL assumes 1 mol of H₂ forms from 2 mol of Mg, and about 209 mL is misled by the coefficient of 2H₂O into assuming 2 mol of H₂ per 1 mol of Mg.