Calcium hydroxide: Difference between revisions
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{{Compound|chemf=Ca(OH)2 | {{Compound|chemf=Ca(OH)2 | ||
|stp_p=solid|stp_q=white | |stp_p=solid|stp_q=white | ||
|mm=74.093|density=2.211|sol_aq=1.73|sol_et=non|eof=−987 | |mm=74.093|mp=580 (decomp)|density=2.211|sol_aq=1.73|sol_et=non|eof=−987 | ||
|group=salts | |group=salts | ||
|nfpa_h=3 | |nfpa_h=3 | ||
| Line 13: | Line 13: | ||
* Whitewash | * Whitewash | ||
==Natural Occurrence== | ==Natural Occurrence== | ||
* Calcium hydroxide '''does | * Calcium hydroxide '''does''' occur naturally as the rare mineral portlandite. | ||
==Hazards== | ==Hazards== | ||
* Calcium hydroxide is alkaline. It can irritate the skin, eyes and lungs and should not be ingested in large quantities. Wash with fresh clean water after contact. | * Calcium hydroxide is alkaline. It can irritate the skin, eyes and lungs and should not be ingested in large quantities. Wash with fresh clean water after contact. | ||
==Character== | |||
* Calcium hydroxide, calcium oxide, and calcium carbonate are three interconvertable calcium compounds. | |||
** Calcium hydroxide can be converted to calcium oxide by heating to 580°C, where it loses one molar equivalent of water equal to approximately 25% of its total mass. | |||
** {{#Chem: Ca(OH)2 { = 580°C} CaO + H2O}} | |||
** Calcium hydroxide can be converted to calcium carbonate by bubbling [[carbon dioxide]] through a solution/suspension of calcium hydroxide | |||
** {{#Chem: Ca(OH)2(aq) + CO2 = CaCO3 + H2O)) | |||
==Synthesis== | ==Synthesis== | ||
===From calcium oxide=== | ===From calcium oxide=== | ||
| Line 24: | Line 32: | ||
# Place the water in the container | # Place the water in the container | ||
# Slowly add the calcium oxide, allowing the water to cool in between additions | # Slowly add the calcium oxide, allowing the water to cool in between additions | ||
#: {{#Chem: CaO (s) + H2O (l) = Ca(OH)2 dH= −63.7 kJ/mol of Calcium}} | |||
# The mixture is calcium hydroxide | # The mixture is calcium hydroxide | ||
==Purification== | ==Purification== | ||
==Testing== | ==Testing== | ||
Latest revision as of 17:09, 27 July 2020
| Chemical formula | Ca(OH)2 |
|---|---|
| OTP appearance | white solid |
| Molar Mass(g/mol) | 74.093 |
| Enthalpy of Formation(kJ/mol) | −987 |
| Density(g/cc) | 2.211 |
| Melting Point(°C) | 580 (decomp) |
| Solubility in water(g/L) | 1.73 |
| Solubility in ethanol(g/L) | non |
| NFPA 704 |  0
3
0
|
| Thermal Decomposition | Calcium hydroxide
580°C CaO,H2O |
Uses
Primary
Secondary
- Whitewash
Natural Occurrence
- Calcium hydroxide does occur naturally as the rare mineral portlandite.
Hazards
- Calcium hydroxide is alkaline. It can irritate the skin, eyes and lungs and should not be ingested in large quantities. Wash with fresh clean water after contact.
Character
- Calcium hydroxide, calcium oxide, and calcium carbonate are three interconvertable calcium compounds.
- Calcium hydroxide can be converted to calcium oxide by heating to 580°C, where it loses one molar equivalent of water equal to approximately 25% of its total mass.
- Ca(OH)2{CaO + H2O580°C}→
- Calcium hydroxide can be converted to calcium carbonate by bubbling carbon dioxide through a solution/suspension of calcium hydroxide
- {{#Chem: Ca(OH)2(aq) + CO2 = CaCO3 + H2O))
Synthesis
From calcium oxide
In ideal conditions (distilled water, pure calcium oxide) this works. Presuming a "part by mass" is 1g, this yields half a mol (37g) of calcium hydroxide.
- Gather a watertight container resistant to alkaline substances
- Gather 9 parts by mass of water
- Gather 28 parts by mass of calcium oxide
- Place the water in the container
- Slowly add the calcium oxide, allowing the water to cool in between additions
- CaO(s) + H2O(l) → Ca(OH)2ΔH=−63.7 kJ/mol of Calcium
- The mixture is calcium hydroxide
Purification
Testing
Storage
- Calcium hydroxide is a caustic alkali, so glass and ceramic containers are excellent. Aluminum in particular is bad.
- Calcium hydroxide will absorb carbon dioxide from the air and precipitate as calcium carbonate, so keep in a sealed container