Zinc hydroxide (Zn(OH)2) is a white, powdery substance formed when zinc reacts with water. It is used in various applications, including as a corrosion inhibitor and in medicinal ointments.
| IUPAC Name | Zinc Hydroxide |
| Molecular Formula | Zn(OH)2 |
| CAS Number | 20427-58-1 |
| Synonyms | Zinc dihydroxide; Zinc(II) hydroxide |
| InChI | InChI=1S/2H2O.Zn/h2*1H2;/q;;+2/p-2 |
Zinc Hydroxide Properties
Zinc Hydroxide Formula
The formula of zinc dihydroxide is Zn(OH)2. It consists of one Zn2+ ion bonded to two OH- ions through ionic bonds. The formula indicates that each zinc ion is surrounded by two hydroxide groups.
Zinc Hydroxide Molar Mass
The molar mass of zinc dihydroxide (Zn(OH)2) is calculated by summing the atomic masses of its constituent elements. Zinc (Zn) has a molar mass of approximately 65.38 g/mol, while the molar mass of one OH- group is about 17.01 g/mol. Therefore, the molar mass of zinc dihydroxide is around 99.42 g/mol.
Zinc Hydroxide Boiling Point
Zinc dihydroxide does not have a distinct boiling point because it decomposes before reaching a boiling temperature. Upon heating, it decomposes into zinc oxide (ZnO) and water (H2O). Therefore, Zinc dihydroxide is more commonly encountered as a solid rather than in its liquid form.
Zinc Hydroxide Melting Point
Zinc dihydroxide has a melting point of approximately 125°C (257°F). At this temperature, the solid Zn(OH)2 transforms into a liquid state. It is essential to handle Zinc dihydroxide with care during heating to prevent its decomposition at higher temperatures.
Zinc Hydroxide Density g/mL
The density of Zinc dihydroxide is approximately 3.05 g/mL. This density value refers to the mass of Zinc dihydroxide per unit volume. The high density indicates that Zinc dihydroxide is a relatively heavy compound.
Zinc Hydroxide Molecular Weight
The molecular weight of Zinc dihydroxide is approximately 99.42 g/mol. It represents the sum of the atomic weights of all atoms present in one molecule of Zn(OH)2, which includes the zinc atom and two hydroxide groups.
Zinc Hydroxide Structure
Zinc dihydroxide has a crystal structure, and it is predominantly found in the form of a white, amorphous powder. The Zn2+ ions are surrounded by two OH- ions in a tetrahedral arrangement.
Zinc Hydroxide Solubility
Zinc dihydroxide is sparingly soluble in water, meaning it dissolves to a limited extent. It can partially dissociate into Zn2+ ions and OH- ions in aqueous solutions. The solubility of Zinc dihydroxide is influenced by factors such as temperature and pH levels.
| Appearance | White powder |
| Specific Gravity | Not applicable |
| Color | White |
| Odor | Odorless |
| Molar Mass | 99.42 g/mol |
| Density | 3.05 g/mL |
| Melting Point | 125°C (257°F) |
| Boiling Point | Decomposes |
| Flash Point | Not applicable |
| Water Solubility | Sparingly soluble |
| Solubility | Partially soluble, partially dissociate into Zn2+ and OH- ions |
| Vapour Pressure | Not applicable |
| Vapour Density | Not applicable |
| pKa | Not applicable |
| pH | Alkaline (basic) |
Zinc Hydroxide Safety and Hazards
Zinc dihydroxide poses certain safety considerations and hazards. When handling this substance, it is crucial to wear appropriate personal protective equipment, such as gloves and eye protection, to avoid skin and eye contact. In case of ingestion or inhalation, seek medical attention immediately. Avoid exposure to high temperatures as it decomposes into hazardous products. Store zinc dihydroxide in a cool, dry place, away from incompatible materials. Additionally, ensure proper ventilation during handling to prevent the buildup of potentially harmful fumes. Always follow safety guidelines and regulations to minimize risks and ensure safe usage.
| Hazard Symbols | Not classified |
| Safety Description | Wear PPE; Avoid contact with skin, eyes, and ingestion; Seek medical attention in case of exposure. |
| UN IDs | Not applicable |
| HS Code | 28161000 |
| Hazard Class | Not classified |
| Packing Group | Not classified |
| Toxicity | Low toxicity |
Zinc Hydroxide Synthesis Methods
Various methods can synthesize zinc dihydroxide.
One common approach involves the reaction between zinc salts, such as zinc chloride or zinc sulfate, and a strong base, typically NaOH or KOH. The reaction proceeds with the displacement of chloride or sulfate ions by OH- ions, resulting in the formation of zinc dihydroxide.
Another method involves the precipitation of zinc dihydroxide from a Zn salt solution using an alkali metal OH. Gradually add an aqueous solution of Zn salt to a solution of sodium hydroxide or potassium hydroxide. This causes the formation of a white precipitate of zinc dihydroxide.
Obtain zinc dihydroxide through the electrolysis of a zinc sulfate solution. Pass an electric current through the solution, causing zinc ions to migrate towards the cathode and react with water molecules, leading to the deposition of zinc dihydroxide on the electrode.
Overall, these synthesis methods provide a route to produce zinc dihydroxide for various industrial, research, and medical applications.
Zinc Hydroxide Uses
Zinc dihydroxide finds a range of applications across diverse fields due to its unique properties. Some key uses include:
- Corrosion inhibitor: Zinc dihydroxide inhibits corrosion in coatings and paints, protecting metal surfaces from oxidation and deterioration, thus extending their lifespan.
- Medicinal ointments: Various medicinal ointments utilize zinc dihydroxide for treating skin conditions like eczema and diaper rash, owing to its antiseptic and astringent properties.
- Active pharmaceutical ingredient (API): In the pharmaceutical industry, drugs used to alleviate stomach disorders, including antacids, incorporate zinc dihydroxide as an active pharmaceutical ingredient.
- Water treatment: Water treatment processes employ zinc dihydroxide as a coagulant to remove impurities and pollutants from water.
- Rubber industry: In the rubber industry, zinc dihydroxide acts as an accelerator in the vulcanization process, enhancing rubber strength and elasticity.
- Adhesives: The formulation of adhesives and glues incorporates zinc dihydroxide to provide improved bonding properties.
- Paint driers: zinc dihydroxide functions as a drier in oil-based paints, hastening the drying process.
- Agriculture: In agriculture, farmers apply zinc dihydroxide as a fungicide to shield crops from diverse fungal diseases.
- Flame Retardants: Manufacturers incorporate zinc dihydroxide as a flame-retardant additive in plastics and textiles, curbing their flammability.
Zinc dihydroxide’s versatile applications make it a valuable compound in numerous industries, contributing to improved product performance and safety.
Questions:
Q: Which substances are acids among the following: AgOH, HF, Ni(OH)2, NH4OH, HMnO4, Zn(OH)2?
A: HF (hydrofluoric acid) and HMnO4 (permanganic acid) are acids.
Q: What is the pH of a saturated solution of Zn(OH)2? Ksp = 1.8 × 10^−14.
A: The pH of a saturated solution of Zn(OH)2 is approximately 7, which is neutral.
Q: If E°cell is -0.762 V, find Ksp for Zn(OH)2?
A: The Ksp for Zn(OH)2 is approximately 4.5 × 10^−17.
Q: What is Zn(OH)2?
A: Zn(OH)2 is zinc dihydroxide, a white powdery substance formed when zinc reacts with water.
Q: Which substance is important in making plastics? Zinc hydroxide, ammonia, acetic acid, nitric acid?
A: None of the substances mentioned are primarily important in making plastics.
Q: Is zinc hydroxide soluble?
A: Zinc dihydroxide is sparingly soluble in water.
Q: What is the chemical formula for zinc hydroxide?
A: The chemical formula for zinc dihydroxide is Zn(OH)2.
Q: What is formed when zinc reacts with sodium hydroxide?
A: When Zn reacts with NaOH, zinc dihydroxide (Zn(OH)2) is formed.
Q: Is zinc hydroxide soluble in water?
A: Zinc dihydroxide is sparingly soluble in water.
Q: Is zinc hydroxide a strong base?
A: Zinc dihydroxide is a weak base.