The chemical formula for lime is:
Try it first: pick an option, then read the explanation.
Understanding Lime and Its Production
In construction, the term "lime" most commonly refers to quicklime. It is a fundamental building material produced by the thermal decomposition of limestone (calcium carbonate). This process, known as calcination, involves heating limestone to a high temperature (above 900°C) to drive off carbon dioxide, leaving behind the chemically reactive quicklime.
Detailed Analysis of the Options
A. CaO
This is the correct answer. CaO is the chemical formula for Calcium Oxide, which is the scientific name for quicklime or simply "lime" in the context of building materials.
C. CaCO₃
This is incorrect. CaCO₃ is the chemical formula for Calcium Carbonate. This is the raw material, limestone, from which lime is produced. It is not lime itself.
B. CaO₂ and D. Ca₂O₃
These are incorrect. These are not the standard chemical formulas for common lime-based building materials. CaO (Calcium Oxide) is the stable oxide of calcium formed during calcination.
Summary: Common Lime-Related Compounds
| Common Name | Chemical Name | Formula |
|---|---|---|
| Lime / Quicklime | Calcium Oxide | CaO |
| Slaked / Hydrated Lime | Calcium Hydroxide | Ca(OH)₂ |
| Limestone / Chalk | Calcium Carbonate | CaCO₃ |
| Gypsum | Calcium Sulphate Dihydrate | CaSO₄·2H₂O |
Study Tips
- Limestone to Lime: Remember the process: Limestone (CaCO₃) is heated, loses CO₂, and becomes Lime (CaO).
- "O" for Oxide: The "O" in CaO stands for Oxide. Quicklime is Calcium Oxide.
- "CO₃" for Carbonate: The "C" in CaCO₃ stands for Carbonate. Limestone is Calcium Carbonate. This is a simple way to distinguish the two most commonly confused formulas.
- Hydrated = Hydroxide: When water is added to lime (hydration), it becomes slaked or hydrated lime, which is Calcium Hydroxide (OH).