Calcium sulfate (CaSO4) is a white powder that occurs naturally or is produced industrially. It is used in construction, food, and medicine due to its properties as a binding agent, filler, and nutrient.
| IUPAC Name | Calcium sulfate |
| Molecular Formula | CaSO4 |
| CAS Number | 7778-18-9 |
| Synonyms | Gypsum, anhydrous gypsum, anhydrite, dihydrate, calcium salt, selenite |
| InChI | InChI=1S/Ca.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 |
Calcium Sulfate Properties
Calcium Sulfate Formula
The chemical formula of calcium sulfate is CaSO4. This means that each molecule of calcium sulfate contains one calcium atom, one sulfur atom, and four oxygen atoms. The formula is used to represent the composition of calcium sulfate in chemical equations and to calculate the amount of reactants required in chemical reactions.
Calcium Sulfate Molar Mass
The molar mass of CaSO4 is approximately 136.14 g/mol. This value is calculated by adding the atomic masses of one calcium atom, one sulfur atom, and four oxygen atoms in the compound. The molar mass is used to determine the amount of CaSO4 required in chemical reactions and to calculate its concentration in solutions.
Calcium Sulfate Boiling Point
CaSO4 does not have a defined boiling point because it undergoes thermal decomposition before reaching its boiling point. However, it can be heated to temperatures above 200°C without undergoing decomposition. At higher temperatures, CaSO4 undergoes endothermic decomposition to form calcium oxide and sulfur trioxide.
Calcium Sulfate Melting Point
The melting point of CaSO4 depends on its hydration state. The anhydrous form of CaSO4 has a melting point of approximately 1460°C, while the dihydrate form has a lower melting point of about 128°C. The hemihydrate and trihydrate forms have intermediate melting points.
Calcium Sulfate Density g/mL
The density of CaSO4 depends on its form and hydration state. The anhydrous form of CaSO4 has a density of approximately 2.96 g/mL, while the dihydrate form has a density of about 2.32 g/mL. The hemihydrate and trihydrate forms have intermediate densities.
Calcium Sulfate Molecular Weight
The molecular weight of CaSO4 is approximately 136.14 g/mol. This value is calculated by adding the atomic masses of one calcium atom, one sulfur atom, and four oxygen atoms in the compound. The molecular weight is used to calculate the amount of CaSO4 required in chemical reactions and to determine its concentration in solutions.
Calcium Sulfate Structure
CaSO4 has a crystalline structure that can vary depending on its hydration state. The anhydrous form of CaSO4 has a crystal structure that is classified as orthorhombic, while the dihydrate form has a monoclinic crystal structure. The hemihydrate and trihydrate forms have different crystal structures that are intermediates between the anhydrous and dihydrate forms.
| Appearance | White powder or solid |
| Specific Gravity | 2.96 (anhydrous), 2.32 (dihydrate) |
| Color | White or colorless |
| Odor | Odorless |
| Molar Mass | 136.14 g/mol |
| Density | 2.96 g/cm³ (anhydrous), 2.32 g/cm³ (dihydrate) |
| Melting Point | 1460°C (anhydrous), 128°C (dihydrate) |
| Boiling Point | Does not have a defined boiling point |
| Flash Point | Not applicable |
| Water Solubility | 0.24 g/100 mL (20°C) |
| Solubility | Soluble in water and glycerol, insoluble in ethanol |
| Vapor Pressure | Negligible |
| Vapor Density | Not applicable |
| pKa | 9.8 (first dissociation), 11.8 (second dissociation) |
| pH | 7 (neutral) |
Calcium Sulfate Safety and Hazards
CaSO4 is generally considered safe to use and handle, but it may pose some health hazards if not handled properly. Inhalation of CaSO4 dust can cause irritation to the respiratory system, while ingestion of large amounts of the compound can cause gastrointestinal upset. Eye and skin contact with CaSO4 may cause irritation or dryness. CaSO4 may also react with certain chemicals to produce hazardous byproducts. Therefore, appropriate personal protective equipment should be worn when handling CaSO4, and it should be stored in a cool, dry, well-ventilated area away from incompatible materials.
| Hazard Symbols | None |
| Safety Description | Harmful if swallowed. Causes skin and eye irritation. |
| UN IDs | Not regulated |
| HS Code | 2833.29.00 |
| Hazard Class | Not classified as a hazardous substance or mixture according to Regulation (EC) No. 1272/2008 [CLP] |
| Packing Group | Not applicable |
| Toxicity | LD50 (oral, rat): > 2000 mg/kg |
Calcium Sulfate Synthesis Methods
Several methods can synthesize CaSO4 depending on the desired form and hydration state of the compound.
One common method is by the reaction of calcium carbonate or calcium oxide with sulfuric acid. The reaction produces CaSO4 and carbon dioxide or water, respectively.
Another method involves the reaction of calcium chloride with sodium sulfate, which results in the precipitation of CaSO4. Thermal dehydration of gypsum, a naturally occurring mineral form of CaSO4 dihydrate, produces CaSO4.
Certain industrial processes, such as the desulfurization of flue gases from power plants, produce CaSO4 as a byproduct. During this process, sulfur dioxide reacts with calcium carbonate to form calcium sulfite, which undergoes oxidation to produce CaSO4.
The synthesis method used for CaSO4 may affect its properties, such as particle size, crystallinity, and purity. Therefore, it is important to choose the appropriate method for the intended application of the compound.
Calcium Sulfate Uses
CaSO4 has a variety of uses in different industries due to its unique properties, including its low toxicity, high melting point, and white color. Some common uses of CaSO4 include:
- Construction: Key component of cement and plasterboard, where it acts as a binder and filler.
- Food and Beverage: Used as a coagulant in the production of tofu, and as a firming agent in certain cheeses and canned vegetables.
- Pharmaceuticals: Used as a filler and binder in the production of tablets and capsules.
- Agriculture: Used as a soil amendment to improve soil structure and increase crop yield.
- Chemicals: Used in the production of various chemicals, such as pigments, paper, and textile processing.
- Cosmetics: Used in cosmetic formulations as a bulking agent and opacifier.
- Water Treatment: Used in water treatment to remove impurities and reduce scaling.
- Plastics and Rubber: Used as a filler and reinforcing agent in plastics and rubber products.
Questions:
Q: Is calcium sulfate vegan?
A: Yes, CaSO4 is considered vegan as it is not derived from animal sources.
Q: What was the principal use of calcium sulfate in hospitals?
A: CaSO4 was commonly used in hospitals as a plaster cast for bone fractures.
Q: What masses of calcium sulfate and phosphoric?
A: This question is incomplete and needs more information to provide a specific answer.
Q: Is CaSO4 soluble in water?
A: CaSO4 has low solubility in water, with a solubility of approximately 2.05 g/L at room temperature.
Q: Is CaSO4 soluble?
A: Calcium sulfate has low solubility in water, with a solubility of approximately 2.05 g/L at room temperature.
Q: What is the molar mass of CaSO4?
A: The molar mass of CaSO4 is approximately 136.14 g/mol.
Q: Which salt has a pH < 7? KBr, HCOOK, CaSO4, NH4NO3
A: None of the listed salts have a pH < 7 in their pure form. However, when dissolved in water, NH4NO3 (ammonium nitrate) will produce an acidic solution with a pH < 7.