Quartz is a substance because the material has uniform properties throughout and is held together via chemical bonds.
Given:
2 Mg + O2 → 2 MgO
So,
<span>(25.0 g of Mg / 24.3051 g/mole) x (1/2) x (22.4 L/mole) = 11.5 L of Oxygen will react with 25 grams of magnesium metal.</span>
