? 發問於 科學及數學化學 · 1 十年前

Chem! Concerning metal reactivity -- 10 pts

1. Why do metals react with water to form metal hydroxide but reacts with steam to form metal oxide? They are of the same constituents.

eg. Mg+2H2O(l) --> Mg(OH)2 +H2

Mg+ H2O(g)--> MgO + H2

更新:

So that means... when steam reacts with metal, a metal hydroxide is formed first, but then the water molecule is boiled away, leaving the metal oxide there? Is this correct?

1 個解答

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  • 1 十年前
    最愛解答

    When metals react with water

    Mg(s) + 2H2O(l) → Mg(OH)2(aq) + H2(g)

    Metal hydroxide is formed

    When metals react with steam

    Mg(s) + H2O(g) → MgO(s) + H2(g)

    Metal oxide is formed instead of metal hydroxide.

    Please note that steam is usually over 100℃, which is the boiling point of water.

    In magnesium hydroxide, a water molecule exist.

    i.e. In Mg(OH)2, you may find a H2O molecule in it.

    So, when steam reacts with metal,

    The water molecule is boiled away.

    That’s why metal oxide is formed instead of metal hydroxide.

    Note that: MgO + H2O → Mg(OH)2

    資料來源: Myself~~~
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