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• Sodium HP

• Potassium HP

• Rubidium HP

• Caesium HP

• Francium HP

• The Alkali Metals

• Reactions

• The Metal Hydroxide

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• Atomic Structure

• Electrovalent Bonding

• Covalent Bonding

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• Transition Metals

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• Noble Gases

Alkali metal hydroxides can be used to test the identity of metals in certain salts.
 

sodium hydroxide + metal salt sodium salt + metal hydroxide ↓

The colour of the precipitate will help identify the metal:

• Calcium hydroxide is soluble; no precipitate is formed

• Copper hydroxide forms a blue precipitate

• Iron II hydroxide forms a green precipitate

• Iron III hydroxide forms a red-brown precipitate

• Zinc hydroxide forms a jelly-like, white precipitate

• Aluminium hydroxide forms a white precipitate that will re-dissolve as the reaction proceeds.

CaSO₄ + 2NaOH  Na₂SO₄ + Ca(OH)₂

FeCl₃+ 3NaOH   3NaCl  +  Fe(OH)₃↓