Magnesium oxide doesn't exist in gaseous form. It occurs naturally in mineral form - as periclase. In refined form - it is a white solid
When magnesium oxide is sufficiently heated, oxygen gas is evolved.
When magnesium is heated, it undergoes a chemical reaction with oxygen in the air, resulting in the release of a gas called magnesium oxide (MgO).
Magnesium oxide don't react with water.
Magnesium carbonate
Hydrogen gas is released when calcium and water react.
16.12-9.72=6.40g
4.03g - 2.43g = 1.60g
Magnesium carbonate
Magnesium Carbonate
2Mg + O2 → 2MgO
2Mg + O2 ---> 2MgO
Magnesium reacts with steam faster than cold water because magnesium needs to burn to get magnesium oxide and to get magnesium oxide there has to be heat and since steam is already heated it doesn't need much time, but the cold water needs time to heat first to react.