Doing an a-level in chemistry and got a recurrent problem. In some books it is stated that magnesium reacts with water to give magnesium oxide when till now I know that it shall have given magnesium hydroxide.. any explanation??

With liquid water, it forms magnesium hydroxide after much time. However, with steam, magnesium oxide is formed and the reaction is very fast.

Thank you for your answer but is it not supposed to be unreactive with water? (only react with steam).. no matter how much time in contact

Well, I was taught that a few amount of hydrogen does collect after a few days with Mg reacting with water.

See here: http://www.lenntech.com/elements-and-water/magnesium-and-water.htm


In what way and in what form does magnesium react with water?

Magnesium metals are not affected by water at room temperature. Magnesium generally is a slow-reacting element, but reactivity increases with oxygen levels. Furthermore, magnesium reacts with water vapor to magnesium hydroxide and hydrogen gas:

Mg (s) + 2H2O(g) -> Mg(OH)2(aq) + H2(g)

Thanks a lot.. u mauritian? mo morisien mo osi!

doing an a-level in chemistry and got a recurrent problem. In some books it is stated that magnesium reacts with water to give magnesium oxide when till now i know that it shall have given magnesium hydroxide.. any explanation?


Magnesium does react with water to form hydrogen. However, magnesium is so reactive that it quickly forms a coating of magnesium hydroxide on its surface. That coating inhibits the reaction of magnesium with water.

Magnesium's hydroxide (or oxide) coat isn't very tough. Aluminum is actually more reactive than magnesium but its oxide coat is so tough that it can't easily be broken down. So, aluminum appears to be nearly unreactive in water.

If, however, you add sodium hydroxide to water and get a solution with a pH greater than about 10 (I think it's about 10. It might be a bit higher), the strong base will attack the magnesium or aluminum oxide coat and break it down. Water will be free to attack the metal and the reaction proceeds very quickly. In other words, you get a lot of hydrogen in a short time.

In most solutions, magnesium will form magnesium hydroxide. If you dry it out, you'll drive off water and form magnesium oxide. You'd probably have to really heat it up a lot to get pure MgO. Otherwise, you'll have a mixture of oxide and hydroxide.

Mg(OH)_2 \, + \, heat \, \rightarrow\, H_2O + MgO

thanks a lot..u mauritian??mo morisien mo osi!

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