Lime = Calcium carbonate = Calcite
Sum formula:
CaCO
3
Calcium carbonate occurs in nature in three crystallized modifications:
Calcite (calcareous spar)
- hexagonal crystallized
Aragonite (pearls)
- rhombic crystallized
Vaterit
- rhombic crystallized
If
calcium
carbonate
precipitates
as
a
poorly
soluble
compound
when
the
solubility
product
is
exceeded
from
aqueous
solutions,
the
precipitate
is
initially
amorphous
and
then slowly changes to the crystalline form of calcite.
When
heated
(burned),
calcium
carbonate
decomposes
to
form
calcium
oxide
(burned
lime) and carbon dioxide:
CaCO
3
→ CaO + CO
2
This
reaction
is
used
for
the
production
of
burnt
lime
and
for
the
production
of
carbon
dioxide.
Calcium
oxide
reacts
with
water
in
a
strongly
exothermic
reaction
to
form
calcium
hydroxide = slaking of lime:
CaO + H
2
O → Ca(OH)
2
Calcium
hydroxide
is
the
main
component
of
lime
mortar.
Calcium
carbonate
is
formed
by reaction with the CO
2
in the air, which then leads to the corresponding strength:
Ca(OH)
2
+ CO
2
→ CaCO
3
+ H
2
O
Linguistically, the term "lime" therefore occurs for different chemical compounds:
CaCO
3
Calcium carbonate - Lime
CaO
Calcium oxide - burnt lime, quicklime
Ca(OH)
2
Calcium hydroxide - Hydrated lime, slaked lime
Common
names
for
naturally
occurring
calcium
carbonate
include
limestone,
chalk,
and
marble.
Lime = Calcite = CaCO
3
Lime as CaCO
3