Editing Calcium hydroxide
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: Ca(OH)<sub>2</sub> → Ca<sup>2+</sup> + 2 OH<sup>−</sup> |
: Ca(OH)<sub>2</sub> → Ca<sup>2+</sup> + 2 OH<sup>−</sup> |
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The solubility is affected by the [[common-ion effect]]. Its solubility drastically decreases upon addition of hydroxide or calcium sources. |
The solubility is affected by the [[common-ion effect]]. Its solubility drastically decreases upon addition of hydroxide or calcium sources. |
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==Reactions== |
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⚫ | When heated to 512 °C, the [[partial pressure]] of water in equilibrium with calcium hydroxide reaches 101{{nbsp}}kPa (normal atmospheric pressure), which [[chemical decomposition|decomposes]] calcium hydroxide into [[calcium oxide]] and water:<ref>{{cite journal |last=Halstead |first=P. E. |author2=Moore, A. E. |title=The Thermal Dissociation of Calcium Hydroxide |journal=Journal of the Chemical Society |volume=769 |pages=3873 |year=1957 |doi=10.1039/JR9570003873}}</ref> |
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When carbon dioxide is passed through limewater, the solution takes on a milky appearance due to [[precipitation (chemistry)|precipitation]] of insoluble [[calcium carbonate]]: |
When carbon dioxide is passed through limewater, the solution takes on a milky appearance due to [[precipitation (chemistry)|precipitation]] of insoluble [[calcium carbonate]]: |
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: Ca(OH)<sub>2</sub>{{sub|({{serif|''aq''}})}} + CO<sub>2</sub>{{sub|({{serif|''g''}})}} → CaCO<sub>3</sub>{{sub|({{serif|''s''}})}} + H<sub>2</sub>O{{sub|({{serif|''l''}})}} |
: Ca(OH)<sub>2</sub>{{sub|({{serif|''aq''}})}} + CO<sub>2</sub>{{sub|({{serif|''g''}})}} → CaCO<sub>3</sub>{{sub|({{serif|''s''}})}} + H<sub>2</sub>O{{sub|({{serif|''l''}})}} |
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If excess CO<sub>2</sub> is added: the following reaction takes place: |
If excess CO<sub>2</sub> is added: the following reaction takes place: |
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: CaCO<sub>3</sub>{{sub|({{serif|''s''}})}} + H<sub>2</sub>O{{sub|({{serif|''l''}})}} + CO<sub>2</sub>{{sub|({{serif|''g''}})}} → [[Calcium bicarbonate|Ca(HCO<sub>3</sub>)<sub>2</sub>]]{{sub|({{serif|''aq''}})}} |
: CaCO<sub>3</sub>{{sub|({{serif|''s''}})}} + H<sub>2</sub>O{{sub|({{serif|''l''}})}} + CO<sub>2</sub>{{sub|({{serif|''g''}})}} → [[Calcium bicarbonate|Ca(HCO<sub>3</sub>)<sub>2</sub>]]{{sub|({{serif|''aq''}})}} |
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The milkiness disappears since calcium bicarbonate is water-soluble. |
The milkiness disappears since calcium bicarbonate is water-soluble. |
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Calcium hydroxide reacts with [[aluminium]]. This reaction is the basis of [[aerated concrete]].<ref name=Ullmann/> It does not corrode [[iron]] and [[steel]], owing to [[passivation (chemistry)|passivation]] of their surface. |
Calcium hydroxide reacts with [[aluminium]]. This reaction is the basis of [[aerated concrete]].<ref name=Ullmann/> It does not corrode [[iron]] and [[steel]], owing to [[passivation (chemistry)|passivation]] of their surface. |
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Limewater turns milky in the presence of [[carbon dioxide]] due to the formation of insoluble [[calcium carbonate]], a process called [[carbonatation]]: |
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⚫ | When heated to 512 °C, the [[partial pressure]] of water in equilibrium with calcium hydroxide reaches 101{{nbsp}}kPa (normal atmospheric pressure), which [[chemical decomposition|decomposes]] calcium hydroxide into [[calcium oxide]] and water:<ref>{{cite journal |last=Halstead |first=P. E. |author2=Moore, A. E. |title=The Thermal Dissociation of Calcium Hydroxide |journal=Journal of the Chemical Society |volume=769 |pages=3873 |year=1957 |doi=10.1039/JR9570003873}}</ref> |
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In a process called [[sulfation]], sulphur dioxide reacts with limewater: |
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: Ca(OH)<sub>2</sub> |
: Ca(OH)<sub>2</sub> → CaO + H<sub>2</sub>O |
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Limewater is used in a process known as [[lime softening]] to reduce water hardness. It is also used as a neutralizing agent in municipal waste water treatment. |
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==Structure and preparation== |
==Structure and preparation== |