no magnesium doesn't react with pure H2O
Burn a piece of magnesium (just did an assessment on that)
Magnesium can burn in the absence of elemental oxygen, yes. This is because it is such a strong reducing agent that it can essentially steal oxygen from substances such as water and carbon dioxide.
Magnesium react with water and burn easily in air.
magnesium oxide
No - phosphorous can not just appear.Heating magnesium hydroxide will give magnesium oxide and water.
magnesium oxide is formed
Yes, magnesium burn in air.
Hydrogen gas is released when calcium and water react.
Magnesium sulfate is not flammable; by heating it is thermally decomposed.
Thermal Burn
No, magnesium can continue tor burn in nitrogen to form magnesium nitride, Mg3N2
Magnesium sulfate is usually just in the ground water to begin with. Too much magnesium sulfate can have dehydration and laxative effects. Several filtration methods can remove magnesium sulfate and other dissolved substances from ground water. That's not to say it being in the water is a bad thing, magnesium is a needed mineral and drinking water that has been filtered can lead to a magnesium deficiency.