Chemical properties of water

by Andreea Verdes, XI B class
“Vasile Alecsandri” High School, Galati, Romania

Experimentally it has been proved that water is a chemical combination very stable. She can be discomposed at over 1000C or with the help of the electrical current.

2H₂O 2H₂+ O₂

Water is very reactive from the chemical way of thinking. She reacts in some conditions with metals, nonmetals, basic oxides, acid oxides.

a) The action of the water with the metals

Metals: potassium, calcium, sodium react violently with water at cold, with forming of hydroxide and degage of hydrogen:

Na + H₂O NaOH + 1/2H₂

Magnesium reacts with water at hot temperatures or in vapor state:

Mg + 2H₂O Mg(OH)₂ + H₂

Aluminum is attacked by water only if it’s clean by the protective layer of oxide:

2Al + 6H₂O 2Al(OH)₃ + 3H₂

Hot steel reacts with water in vapor state and it forms the ferro-ferric oxide

3Fe + 4H₂O Fe₃O₄ + 4H₂

Plumb, cupper, mercury, gold, silver aren’t attacked by water or the vapors of water.

Some metals corrode at the presence of water. The attack is more powerful in the presence of the oxygen and the dioxide of carbon.

b) The action of the water with the nonmetals

Chlorine in reaction with water forms the chlorine water:

Cl₂ + H₂O HCl + HClO

HClO HCl + [O]

Passing a current of vapours of water over the coke at the temperature of almost 1000C it forms a mixture of monoxide of carbon and hydrogen, named water gaze. The reaction has an industrial importance:

C + H₂O CO + H₂

c) The action of water with oxides

Water reacts with metallic soluble oxides with formation of hydroxides.

One of the reactions of practical importance is constituted of the extinguishing of the chalk, reaction powerfully exothermal.

CaO + H₂O Ca(OH)₂ + Q

The hydroxide of calcium obtained is relatively little soluble in water and this is why at the extinguishing of the chalk it is obtained the so named milk of chalk, which represents a fine suspension of Ca(OH)₂ in a saturated solution of hydroxide of calcium.

At the dissolving of hydroxide of sulphur in water it takes place a chemical reaction from which it results an acid solution, sulphurous acid.

SO₂ + H₂O H₂SO₃

The reaction with carbide or carbora of calcium at CaC2 goes to the reaction of the forming of acetylene, organic substance utilized at the welding and the cut of metals in the oxyacetylene machine:

CaC₂ + 2H₂O HCCH + Ca(OH)₂ + Q