Page 27 - Curriculum Visions Dynamic Book

Green copper coating
Copper corrodes in moist air due to the combined effects of copper, water, oxygen and carbon dioxide from the air.
This makes a pleasing green copper carbonate coating known as a patina, or incrustation. A patina protects the surface of a substance from further attack, and forms
on copper, brass and bronze objects.
gelatinous: a term meaning made with water. Because a gelatinous precipitate
is mostly water, it is of a similar density
to water and will float or lie suspended
in the liquid.
patina: a surface coating that develops on metals and protects them from further corrosion.
EQUATION: How copper develops a green colour when exposed to the environment
Copper + carbon dioxide + oxygen (dissolved in water) ➪ copper carbonate 2Cu(s) + 2CO2(g) + O2(aq) ➪ 2CuCO3(s)
 The Statue
of Liberty has
a green copper carbonate coating.
 Preparing blue copper hydroxide
Blue copper hydroxide gelatinous solid is formed by reaction of a copper sulphate solution with a sodium hydroxide solution.
This precipitate shows where the drop of sodium hydroxide solution has reacted with the copper sulphate to produce
a blob of copper hydroxide exactly
the same shape as the drop that entered the solution.
EQUATION: Producing copper hydroxide
Copper sulphate + sodium hydroxide ➪ copper hydroxide + sodium sulphate CuSO4(aq) + 2NaOH(aq) ➪ Cu(OH)2(s) + Na2SO4(aq)
precipitate
Precipitate
 Gelatinous light blue copper hydroxide is changed to a soluble, very dark blue
copper compound when concentrated ammonia
solution is added.
2+
 A representation of
the structure of the copper complex that is formed when excess ammonia solution is added to copper hydroxide.
Oxygen
◆ Copper Nitrogen
Hydrogen
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