Calcium carbide is a chemical compound with the formula CaC2. It is mainly used to produce acetylene gas and calcium cyanamide. It reacts with water to produce acetylene gas and calcium hydroxide. People use it for welding and lighting.
| IUPAC name | Calcium ethynediide |
| Molecular formula | CaC2 |
| CAS number | 75-20-7 |
| Synonyms | Calcium acetylide, calcium percarbide, calcium dicarbide, carbure de calcium, carburo calcico, ethynediide de calcium |
| InChI | InChI=1S/C2.Ca/c1-2;/q-2;+2 |
Calcium Carbide Properties
Calcium Carbide Formula
The chemical formula of calcium carbide is CaC2. This means that one molecule of calcium carbide consists of one atom of calcium and two atoms of carbon. The formula shows the ratio of the elements in the compound.
Calcium Carbide Molar Mass
The molar mass of CaC2 is 64.099 g/mol. This means that one mole of CaC2 has a mass of 64.099 grams. The molar mass is calculated by adding the atomic masses of the elements in the formula. The atomic mass of calcium is 40.078 g/mol and the atomic mass of carbon is 12.011 g/mol.
Calcium Carbide Boiling Point
The boiling point of CaC2 is 2300 °C. This means that CaC2 changes from liquid to gas at this temperature. The boiling point is influenced by intermolecular forces and the atmospheric pressure. CaC2 has strong ionic bonds that require a lot of energy to break.
Calcium Carbide Melting Point
The melting point of CaC2 is 2160 °C. This means that CaC2 changes from solid to liquid at this temperature. The melting point is also influenced by intermolecular forces and the atmospheric pressure. CaC2 has a high melting point because of its strong ionic bonds.
Calcium Carbide Density g/ml
The density of CaC2 is 2.22 g/ml. This means that one milliliter of CaC2 has a mass of 2.22 grams. The density is calculated by dividing the mass by the volume. The density depends on the packing and arrangement of the atoms or molecules in the substance. CaC2 has a high density because its atoms are closely packed in a crystalline structure.
Calcium Carbide Molecular Weight
The molecular weight of CaC2 is 64.099 amu (atomic mass units). This means that one molecule of CaC2 has a mass of 64.099 amu. The molecular weight is calculated by multiplying the atomic masses of the elements in the formula by their respective numbers of atoms. The atomic mass of calcium is 40.078 amu and the atomic mass of carbon is 12.011 amu.
Calcium Carbide Structure
The structure of CaC2 is tetragonal, monoclinic, or monoclinic depending on the phase (I, II, or III). This means that CaC2 has different shapes and arrangements of its atoms or molecules in different states or conditions. The structure is determined by the symmetry and geometry of the substance. CaC2 has a tetragonal structure in phase I, a monoclinic structure in phase II, and another monoclinic structure in phase III.
Calcium Carbide Solubility
The solubility of CaC2 is rapid hydrolysis in water. This means that CaC2 reacts with water quickly and forms acetylene gas and calcium hydroxide as products. The solubility is measured by the amount of substance that can dissolve in a given solvent at a given temperature and pressure. The solubility depends on the nature and polarity of the substance and the solvent, as well as other factors such as pH and salinity.
| Appearance | White powder to grey/black crystals or colorless crystalline solid3 |
| Specific gravity | 2.22 |
| Color | Colorless (pure) or grey/brown (technical-grade) |
| Odor | Odorless (pure) or garlic-like (technical-grade) |
| Molar mass | 64.099 g/mol |
| Density | 2.22 g/cm3 |
| Melting point | 2160 °C |
| Boiling point | 2300 °C |
| Flash point | 305 °C (acetylene) |
| Water solubility | Rapid hydrolysis |
| Solubility | Insoluble in ethanol and ether |
| Vapour pressure | Negligible |
| Vapour density | 2.21 (acetylene) |
| pKa | Not applicable |
| pH | Not applicable |
Calcium Carbide Safety and Hazards
CaC2 is a flammable and dangerous chemical. It can cause fire and explosion hazards when it contacts water or moisture. It releases acetylene gas, which is also flammable and explosive. CaC2 can also harm your health. It can irritate your skin, eyes, and lungs. It can cause skin rash, eye damage, coughing, and shortness of breath. It can also cause fluid build-up in your lungs if you inhale a lot of it. You should avoid contact with CaC2 and wear protective equipment when handling it. You should also store it in a dry and closed container away from any sources of ignition.
| Hazard symbols | F (highly flammable), C (corrosive), W (reacts with water) |
| Safety description | S2 (keep out of reach of children), S7/8 (keep container tightly closed and dry), S16 (keep away from sources of ignition), S26 (in case of contact with eyes, rinse immediately with plenty of water and seek medical advice), S36/37/39 (wear suitable protective clothing, gloves and eye/face protection), S43 (in case of fire, use dry sand or dry chemical powder), S45 (in case of accident or if you feel unwell, seek medical advice immediately) |
| UN IDs | UN 1402 |
| HS code | 28491000 |
| Hazard class | 4.3 |
| Packing group | I |
| Toxicity | LD50 oral rat: 80 mg/kg, LC50 inhalation rat: 1000 ppm/4h |
Calcium Carbide Synthesis Methods
There are different methods to synthesize CaC2 from calcium oxide and carbon sources.
One of the most common methods is the electric arc furnace method. In this process, an electric arc heats a blend of lime and coke to around 2200°C. The reaction is endothermic and produces molten CaC2 and carbon monoxide. After melting, the CaC2 cools down and people crush it into either lumps or powder, depending on their intended use. This method has a high energy consumption and equipment cost.
Another method is the solid-state method. To perform this method, heat a mixture of calcium oxide and biochar or biomass-derived char in a furnace at approximately 1750 °C. The reaction is solid-solid and produces solid CaC2 and carbon monoxide. You can directly use or further process the solid CaC2. This method has a lower energy consumption and equipment cost than the electric arc furnace method.
A third method is the coal coke electricity grading substitution method. To carry out the process, one mixes low-rank coal and lime, forms pellets, and then pyrolyzes them in a furnace at 1000°C. The gas produced generates electricity, and one transfers the hot pellets to a CaC2 furnace at 2000°C. The reaction is solid-solid and produces molten CaC2 and carbon monoxide. After cooling, the molten CaC2 undergoes crushing to form lumps or powder. This method has a high energy efficiency and resource utilization than the electric arc furnace method.
Calcium Carbide Uses
- When CaC2 reacts with water, it produces acetylene gas and calcium hydroxide. Acetylene gas is an important intermediate for the synthesis of many organic chemicals and polymers, such as polyvinyl chloride, vinyl acetate, 1,4-butanediol, etc. Calcium hydroxide is a versatile compound with many uses.
- To produce calcium cyanamide, people react to CaC2 with nitrogen at high temperatures. Calcium cyanamide works as a nitrogen fertilizer, herbicide, and defoliant.
- To reduce the sulfur content in iron, pig iron, cast iron, and steel, people use CaC2. This chemical compound reacts with sulfur to form calcium sulfide, effectively desulfurizing the metal. This process improves the quality and ductility of iron and steel products.
- Carbide lamps use CaC2 to produce acetylene gas, which when burned, generates light. These lamps were popular in the mining, caving, cycling, and automobile industries before electric lamps became common.
- People use CaC2 as a ripening agent for fruits like bananas, mangoes, and papayas. It releases ethylene gas, which accelerates the ripening process and enhances the color and sweetness of the fruits. Many countries consider the practice of using CaC2 residues to ripen fruits as illegal and harmful due to associated health risks.
- People use CaC2 in bamboo cannons and big-bang cannons to make loud noises. When mixed with water, it produces acetylene gas that ignites to create a fun and celebratory experience for everyone.
- Also used as a deoxidizer in the manufacturing of steel. It removes oxygen from the molten steel and prevents the formation of oxides that can impair the quality of steel products.
Questions:
Q: Where to buy calcium carbide locally?
A: You may be able to find small quantities of CaC2 in your area from some hardware stores or welding supply shops. However, if you need large quantities of CaC2, it may be preferable to import it directly from the manufacturers. You can contact some online suppliers.
Q: How do you dispose of calcium carbide?
A: CaC2 is a hazardous waste and should be disposed of properly. You should not dump it in the trash or down the drain, as it can react with water and produce acetylene gas, which is flammable and explosive. You should contact your local hazardous waste management authority or a licensed waste disposal company for guidance on how to safely dispose of CaC2. One may need to neutralize it with water in a well-ventilated area and then pack it in a sealed container for transportation.
Q: What is formed when calcium carbide reacts with heavy water?
A: Heavy water is water that contains deuterium instead of hydrogen. Deuterium is an isotope of hydrogen that has one proton and one neutron in its nucleus. When CaC2 reacts with heavy water, it forms calcium hydroxide and deuterated acetylene. Deuterated acetylene is acetylene that contains deuterium instead of hydrogen. The chemical equation for this reaction is:
CaC2 + 2D2O -> Ca(OD)2 + C2D2
Q: Is calcium carbide dangerous?
A: Yes, CaC2 is dangerous and should be handled with care. It can cause fire and explosion hazards when it contacts water or moisture, as it releases acetylene gas, which is also flammable and explosive. It can also harm your health, as it can irritate your skin, eyes, and lungs. CaC2 can cause skin rash, eye damage, coughing, and shortness of breath. It can also cause fluid build-up in your lungs if you inhale a lot of it. You should avoid contact with CaC2 and wear protective equipment when handling it. You should also store it in a dry and closed container away from any sources of ignition.
Q: Is calcium carbide ionic or covalent?
A: CaC2 is an ionic compound. It consists of calcium ions (Ca2+) and carbide ions (C22-). Ionic compounds are formed when metal atoms lose electrons and nonmetal atoms gain electrons to achieve stable electron configurations. The resulting ions are held together by electrostatic forces of attraction. CaC2 has strong ionic bonds that require a lot of energy to break.
Q: How calcium carbide is made?
A: CaC2 is made by heating a mixture of lime (calcium oxide) and coke (carbon) at about 2200 °C in an electric arc furnace. The reaction is endothermic and produces molten CaC2 and carbon monoxide. The molten CaC2 is then cooled and crushed into lumps or powder. This method has a high energy consumption and equipment cost. There are also other methods that use different sources of carbon, such as biochar or low-rank coal, and different heating methods, such as solid-state heating or induction heating. These methods may have lower energy consumption and equipment cost than the electric arc furnace method.
Q: Can i turn calcium carbonate into calcium carbide?
A: No, you cannot turn calcium carbonate into CaC2 directly. Calcium carbonate is a stable compound that does not react with carbon at high temperatures. You need to convert calcium carbonate into calcium oxide first by heating it strongly in the absence of air (calcination). Then you can react calcium oxide with carbon at high temperatures to produce CaC2 (carburation). The overall chemical equation for this process is:
CaCO3 -> CaO + CO2
CaO + 3C -> CaC2 + CO
Q: What is true for the following reaction? Ca(s) + 2C(s) -> CaC2(s) + 62.8 kJ
A: The following statements are true for the reaction:
- It is a synthesis reaction, where two or more elements combine to form a compound.
- It is an exothermic reaction, where heat is released to the surroundings.
- It is a redox reaction, where calcium is oxidized and carbon is reduced.
- It is the reverse reaction of the formation of CaC2 from calcium oxide and carbon.
Q: What is the standard heat of formation of cac2(s)?
A: The standard heat of formation of cac2(s) is the enthalpy change when one mole of CaC2 is formed from its elements in their standard states at 25 °C and 1 atm. It can be calculated from the given thermochemical equations by using Hess’s law. The overall equation for the formation of CaC2 is:
Ca(s) + 2C(s) -> CaC2(s)
Using Hess’s law, we can write:
ΔHf°(CaC2) = ΔH°(Ca + 2C -> CaC2)
= ΔH°(Ca + 2H2O -> Ca(OH)2 + H2) + ΔH°(Ca(OH)2 -> CaO + H2O) + ΔH°(CaO + 3C -> CaC2 + CO) + ΔH°(CO -> C + O2) + ΔH°(H2 + O2 -> H2O)
= -414.79 kJ + 65.19 kJ + 462.30 kJ – 221.00 kJ – 571.80 kJ = -680.10 kJ
Therefore, the standard heat of formation of cac2(s) is -680.10 kJ/mol.
Q: How many grams of cac2 would be required to generate 0.35 moles of hcch(g)?
A: To answer this question, we need to use the balanced equation for the reaction between CaC2 and water:
CaC2(s) + 2H2O(l) -> C2H2(g) + Ca(OH)2(aq)
From this equation, we can see that one mole of cac2 produces one mole of hcch (also known as acetylene). Therefore, to generate 0.35 moles of hcch, we need 0.35 moles of cac2. To convert moles to grams, we need to use the molar mass of cac2, which is 64.099 g/mol. Multiplying moles by molar mass, we get:
0.35 mol x 64.099 g/mol = 22.435 g
Therefore, we need 22.435 grams of cac2 to generate 0.35 moles of hcch.
Q: How many moles of cac2 are needed to react completely with 49.0g h2o?
A: To answer this question, we need to use the balanced equation for the reaction between calcium carbide and water:
CaC2(s) + 2H2O(l) -> C2H2(g) + Ca(OH)2(aq)
From this equation, we can see that one mole of cac2 reacts with two moles of h2o. Therefore, to find the moles of cac2 needed, we need to divide the moles of h2o by two. To convert grams to moles, we need to use the molar mass of h2o, which is 18.015 g/mol. Dividing grams by molar mass, we get:
49.0 g / 18.015 g/mol = 2.72 mol
Dividing this by two, we get:
2.72 mol / 2 = 1.36 mol
Therefore, we need 1.36 moles of cac2 to react completely with 49.0g h2o.
Q: What are the products of the reaction between calcium carbide and water?
A: The products of the reaction between CaC2 and water are acetylene gas and calcium hydroxide solution.