Neco 2022 Chemistry Question 4

A student determines the molar mass of an unknown metal by reacting a weighed sample with excess hydrochloric acid and collecting the hydrogen gas released over water. **Data recorded** - Mass of metal sample: 0.250 g - Volume of gas collected (over water): 250.0 mL - Temperature of the gas: 25 °C - Atmospheric pressure: 760 mm Hg - Water‑vapour pressure at 25 °C: 23.8 mm Hg The reaction is assumed to be: \(\text{M} + 2\text{HCl} \rightarrow \text{MCl}_2 + \text{H}_2\) (One mole of metal yields one mole of H₂.) The student is required to calculate the molar mass of the metal and identify it from the list: magnesium (Mg, 24.3 g mol⁻¹), zinc (Zn, 65.4 g mol⁻¹), iron (Fe, 55.8 g mol⁻¹), aluminium (Al, 27.0 g mol⁻¹).