Zinc oxide (ZnO) is a white powder that is used in various applications, such as sunscreens, ceramics, and rubber manufacturing, due to its UV-blocking and antimicrobial properties.
| IUPAC Name | Zinc oxide |
| Molecular Formula | ZnO |
| CAS Number | 1314-13-2 |
| Synonyms | Zinc white, Chinese white, philosopher’s wool, Oxozinc |
| InChI | InChI=1S/O.Zn |
Zinc Oxide Properties
Zinc Oxide Formula
The formula of zinc oxide is ZnO. It consists of one zinc atom (Zn) and one oxygen atom (O) chemically bonded together. This simple formula represents the composition of ZnO in its purest form.
Zinc Oxide Molar Mass
The molar mass of ZnO can be calculated by adding the atomic masses of zinc and oxygen. Zinc has an atomic mass of approximately 65.38 g/mol, while oxygen has an atomic mass of around 16.00 g/mol. Adding these values gives a molar mass of approximately 81.38 g/mol for ZnO.
Zinc Oxide Boiling Point
Zinc oxide does not have a well-defined boiling point because it undergoes sublimation at high temperatures. Sublimation is the process in which a solid directly converts into a gas without passing through the liquid phase. For ZnO, this occurs at temperatures above 1800°C (3272°F).
Zinc Oxide Melting Point
The melting point of ZnO is relatively high compared to many other compounds. It melts at around 1975°C (3587°F). At this temperature, the solid ZnO transforms into a liquid state, allowing for various applications that involve its molten form.
Zinc Oxide Density g/ml
The density of ZnO is approximately 5.61 g/ml. This value indicates the mass of ZnO present in a given volume. The high density of ZnO is attributed to its closely packed structure, which contributes to its solid-state properties.
Zinc Oxide Molecular Weight
The molecular weight of ZnO is calculated by summing the atomic weights of its constituent elements, zinc, and oxygen. As mentioned earlier, zinc has an atomic weight of approximately 65.38 g/mol, while oxygen has an atomic weight of around 16.00 g/mol. The molecular weight of ZnO is thus approximately 81.38 g/mol.
Zinc Oxide Structure
Zinc oxide has a hexagonal crystal structure, forming tightly-packed layers of zinc and oxygen atoms. This arrangement gives rise to its characteristic properties. The crystal lattice of ZnO contributes to its stability and various applications in fields such as electronics, ceramics, and coatings.
Zinc Oxide Solubility
Zinc oxide exhibits low solubility in water. It is considered insoluble, with a solubility of less than 0.01 g/100 mL of water. This limited solubility contributes to the stability and longevity of ZnO in various applications, such as in sunscreens, where it provides long-lasting protection against harmful UV rays.
| Appearance | White powder |
| Specific Gravity | 5.61 g/mL |
| Color | White |
| Odor | Odorless |
| Molar Mass | 81.38 g/mol |
| Density | 5.61 g/cm³ |
| Melting Point | 1975°C (3587°F) |
| Boiling Point | Sublimes at high temps |
| Flash Point | Not applicable |
| Water Solubility | Insoluble |
| Solubility | Insoluble in water but soluble in dilute acids and bases |
| Vapor Pressure | Negligible |
| Vapor Density | Not available |
| pKa | Not applicable |
| pH | ~7 |
Zinc Oxide Safety and Hazards
Zinc oxide is generally considered safe for various applications, but it is important to be aware of potential hazards. In its solid form, ZnO is not highly toxic and poses minimal risks. However, inhalation of fine ZnO particles should be avoided as it can cause respiratory irritation. Prolonged or repeated exposure to ZnO dust may lead to a condition known as metal fume fever. It is recommended to handle ZnO with proper ventilation and avoid direct contact with the eyes and skin. Additionally, protective measures such as gloves and goggles should be used when working with concentrated solutions of ZnO.
| Hazard Symbols | None |
| Safety Description | – Avoid inhalation of particles.\n- Handle with proper ventilation.\n- Use protective measures (gloves, goggles).\n- Avoid direct contact with eyes and skin. |
| UN IDs | Not applicable |
| HS Code | 2817.00.00 |
| Hazard Class | Not classified |
| Packing Group | Not applicable |
| Toxicity | Low |
Zinc Oxide Synthesis Methods
There are several methods for synthesizing ZnO. In the direct method, heating zinc metal occurs in the presence of oxygen. The zinc metal oxidizes to form ZnO, which can be collected as a powder.
In the indirect method, you use zinc salts like zinc nitrate or zinc sulfate as starting materials, and then decompose or react them with other compounds to produce ZnO.
Additionally, the precipitation method involves mixing zinc salts with a precipitating agent, such as sodium hydroxide or ammonium carbonate, resulting in the formation of a ZnO precipitate. The hydrothermal method utilizes high-pressure and high-temperature conditions to promote the reaction between zinc salts and a hydroxide source, leading to the formation of ZnO crystals.
Sol-gel synthesis involves the hydrolysis of a zinc precursor, such as zinc acetate, followed by a condensation reaction to form a gel. To obtain ZnO, heat the gel.
Researchers utilize additional techniques, including spray pyrolysis, vapor deposition, and electrodeposition, to create ZnO with tailored characteristics. Each method offers advantages in terms of control over particle size, morphology, and purity, allowing for the tailored synthesis of ZnO for various applications.
Zinc Oxide Uses
Zinc oxide finds numerous applications across various industries due to its versatile properties. Here are some key uses of ZnO:
- Sunscreens: Zinc oxide is a common ingredient in sunscreens as it provides effective protection against harmful UV rays by reflecting and scattering them away from the skin.
- Cosmetics: Cosmetics manufacturers use ZnO in foundations, powders, and creams to absorb excess oil, provide a matte finish, and act as a bulking agent and pigment.
- Pharmaceuticals: Medical creams and ointments utilize ZnO for treating various skin conditions like rashes, burns, and irritations due to its soothing and antimicrobial properties.
- Rubber Industry: The rubber industry employs ZnO as an activator in the vulcanization process, enhancing the strength and durability of rubber.
- Ceramics: Manufacturers incorporate ZnO as a fluxing agent in ceramics production, reducing the melting point and improving the material’s overall properties.
- Electronics: Electronic devices, such as varistors, sensors, and transistors, utilize ZnO as a semiconductor material.
- Paints and Coatings: Paints and coatings contain ZnO as a pigment and UV absorber, ensuring color stability and protecting against sunlight degradation.
- Textiles: Enhancers incorporate ZnO into fabrics and fibers, imparting antimicrobial and odor-reducing properties, rendering them suitable for sportswear, socks, and undergarments.
- Adhesives: Adhesive formulations incorporate ZnO for its bonding strength and heat resistance properties.
- Animal Feed: Animal feed incorporates ZnO as a supplement to address zinc deficiency in livestock, fostering growth and enhancing overall health.
These diverse applications highlight the wide-ranging benefits of ZnO in various industries, making it a valuable and versatile compound.
Questions:
Q: How is zinc sulfate produced?
A: Zinc sulfate is produced by reacting ZnO with sulfuric acid.
Q: What is the use of zinc oxide?
A: ZnO is used in various applications such as sunscreens, cosmetics, pharmaceuticals, rubber manufacturing, ceramics, and electronics.
Q: What percentage of zinc oxide should be in sunscreen?
A: The recommended percentage of ZnO in sunscreen is typically between 10% and 20%.
Q: How to strap a knee with zinc oxide tape?
A: To strap a knee with ZnO tape, start by applying an anchor strip below the knee, then wrap the tape diagonally over the knee and finish with an anchor strip above the knee.
Q: How to use zinc oxide tape for a lateral ligament sprain?
A: To use ZnO tape for a lateral ligament sprain, apply the tape in a figure-eight pattern around the affected area to provide support and stability.
Q: Is zinc oxide safe?
A: ZnO is generally considered safe for use in various applications, but precautions should be taken to avoid inhalation of fine particles.
Q: What is zinc oxide?
A: It is a white powder compound that consists of zinc and oxygen atoms, with the chemical formula ZnO.
Q: What is zinc oxide used for?
A: ZnO is used in sunscreens, cosmetics, ceramics, electronics, pharmaceuticals, and rubber manufacturing due to its UV-blocking, antimicrobial, and other beneficial properties.
Q: How do zinc oxide and titanium dioxide protect your skin?
A: ZnO and titanium dioxide protect the skin by reflecting and scattering UV rays, acting as physical barriers to prevent sunburn and damage caused by sun exposure.