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The Periodic Table

The Alkaline Earth Metals  - Reaction with Water.

How does Magnesium React with Water?

Magnesium will not react with cold water.
Even finely powdered magnesium reacts only very slowly.

Magnesium will react with gaseous water (steam) to
form magnesium oxide and hydrogen gas.
You must know how to test for hydrogen gas.

magnesium  +  steam    magnesium oxide  +  hydrogen.
Mg_(s)     +  H₂O_(g)              MgO_(s)        +    H_2(g)

Magnesium oxide is a base. It will not dissolve in water.

How does Calcium React with Water?

Calcium (and the metals below calcium in group 2)
will react with cold water. They will sink
as they react, unlike the group 1 metals which float.

calcium  +  water     calcium hydroxide  +  hydrogen.
Ca_(s)  +  2H₂O_(l)            Ca(OH)_2(s)      +        H_2(g)

Calcium hydroxide is called slaked lime. Calcium hydroxide will
dissolve a little in water to form lime water (see the previous page).

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