Calcium oxide: Difference between revisions
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JeffEvarts (talk | contribs) (Created page with "{{Compound|name=Calcium oxide|chemf=CaO|mm=56.0774|density=3.34|mp=2613|bp=2850|stp_p=solid|stp_q=white|nfpa_h=3|nfpa_r=2}} ==Uses== ===Primary=== * Feedstock for calcium hy...") |
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*: {{#Chem: CaCO3 = CaO + CO2 | t>800 | dh=178k}} | *: {{#Chem: CaCO3 = CaO + CO2 | t>800 | dh=178k}} | ||
# Place 100 units by mass of calcium carbonate in a lidded ceramic container | # Place 100 units by mass of calcium carbonate in a lidded ceramic container | ||
# Place the container in the [[lime kiln]] | # Repeat | ||
# | ## Place the container in the [[lime kiln]] | ||
# Remove from fire and measure mass.<br>'''N.B.''' You can use the weight loss to estimate total time to conversion: 100 → 90 is 10 units (out of 44) of mass removed. Estimate 2 hrs to convert all. | ## Heat to 900°C (orange heat) for 30 minutes | ||
# | ## Remove from fire and measure mass.<br>'''N.B.''' You can use the weight loss to estimate total time to conversion: 100 → 90 is 10 units (out of 44) of mass removed. Estimate 2 hrs to convert all. | ||
# until mass is 56-57 units. | |||
#: '''NB:''' The above presumes ''pure'' calcium carbonate as feedstock. Impurities may increase or decrease the target weight. | |||
# The material is now mostly calcium oxide. | # The material is now mostly calcium oxide. | ||
==Purification== | ==Purification== | ||
==Testing== | ==Testing== | ||
Revision as of 21:59, 12 December 2019
| Chemical formula | CaO |
|---|---|
| OTP appearance | white solid |
| Molar Mass(g/mol) | 56.0774 |
| Density(g/cc) | 3.34 |
| Melting Point(°C) | 2613 |
| Boiling Point(°C) | 2850 |
| NFPA 704 |  0
3
2
|
Uses
Primary
- Feedstock for calcium hydroxide, lye, and all other hydroxides
Secondary
- Heat without fire:
- CaO(s) + H2O(l) → Ca(OH)2(aq) (ΔHr = −63.7 kJ/mol of CaO)
Natural occurrence
- Does not occur naturally
Hazards
- Corrosive to skin
- Calcium oxide dust irritates the eyes and lungs
- Mixed with water produces substantial heat as well as calcium hydroxide which is caustic.
Production
From calcium carbonate
- Calcium oxide is produced by heating calcium carbonate above 550°C, often in a lime kiln.
- CaCO3 → CaO + CO2
- Place 100 units by mass of calcium carbonate in a lidded ceramic container
- Repeat
- Place the container in the lime kiln
- Heat to 900°C (orange heat) for 30 minutes
- Remove from fire and measure mass.
N.B. You can use the weight loss to estimate total time to conversion: 100 → 90 is 10 units (out of 44) of mass removed. Estimate 2 hrs to convert all.
- until mass is 56-57 units.
- NB: The above presumes pure calcium carbonate as feedstock. Impurities may increase or decrease the target weight.
- The material is now mostly calcium oxide.
Purification
Testing
Storage
Calcium oxide decomposes when exposed to air along two routes:
- Absorb carbon dioxide from the air to become calcium carbonate
- CaO + CO2 → CaCO3
- Absorb water from the air to become calcium hydroxide
- CaO + H2O → Ca(OH)2
Thus, storage is a problem. For these reasons, calcium oxide is most often used as quickly as it is produced.