Why does hot steam produce MgO instead of Mg(OH)2?

**Background research**


* Magnesium hydroxide exists naturally as brucite ([source: wiki](http://en.wikipedia.org/wiki/Magnesium_hydroxide#Preparation))
* Passing hot steam over magnesium produces magnesium oxide (source: [Edexcel's June 2014 Unit 2 exam (CH02\_01): question 18](http://freeexampapers.com/?dir=A-Level/Chemistry/Edexcel/2014-Jun))


**Question**


Why doesn't magnesium hydroxide form when treated with hot steam, instead of magnesium oxide?




There are two steps in the process:


$\ce{Mg + H2O -> MgO + H2}$


and


$\ce{MgO + H2O <-> Mg(OH)2}$


The equilibrium point in the second step is dependent on the temperature. See file [Equilibrium Assemblages](http://www.nsm.buffalo.edu/courses/gly206/StableAssemblages.pdf) for more information.


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$\ce{Mg(OH)2}$ decomposes at high temps into $\ce{MgO}$ and $\ce{H2O}$. To be exact, 350 C


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