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The Alkali Metals - Group 1 - Reaction with Water.
How do the Alkali Metals React with Water?
The alkali
metals lithium, sodium and
potassium all react with
cold
water forming a soluble alkaline hydroxide and hydrogen gas.
You must know how to test for hydrogen gas!
All three metals are less dense
than water and so they float.
How does Sodium React with Water?
Sodium melts and
forms a floating ball of metal
which fizzes
as it moves over the surface of the water giving off hydrogen
gas.
sodium + water
sodium
hydroxide + hydrogen.
2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)
How does Lithium React with Water?
Lithium is less
reactive than sodium and does not
melt but
does react quickly with
cold water giving off hydrogen gas.
lithium + water
lithium
hydroxide + hydrogen.
2Li(s) + 2H2O(l) 2LiOH(aq)
+ H2(g)
How does Potassium React with Water?
Potassium is the most reactive. It
melts, reacts vigorously
and burns
with a lilac flame as it gives off hydrogen gas. Potassium is
dangerous and can explode
when it comes into contact with water.
potassium + water
potassium
hydroxide +
hydrogen.
2K(s) + 2H2O(l) 2KOH(aq)
+ H2(g)
All the hydroxides are strongly alkaline. Note the state
symbol
(aq) after the hydroxide, showing that it is dissolved in water.
The alkali
metals are so named because they form
alkaline hydroxides in water. The metals
themselves are not alkalis, they
are just metals (neutral).
Links Alkali Metals Revision Questions
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