Magnesium hydroxide (Mg(OH)2) is an antacid and laxative used to treat heartburn, indigestion, and constipation. It works by neutralizing stomach acid and drawing water into the colon to promote bowel movements.
| IUPAC Name | Magnesium hydroxide |
| Molecular Formula | Mg(OH)2 |
| CAS Number | 1309-42-8 |
| Synonyms | Milk of magnesia; Brucite; Magnesium dihydroxide; Hydromagnesite; Magnesia alba |
| InChI | InChI=1S/2H2O.Mg/h2*1H2;/q;;+2/p-2 |
Magnesium Hydroxide Properties
Magnesium Hydroxide Formula
The chemical formula for magnesium hydroxide is Mg(OH)2. This formula indicates that one magnesium atom is bonded to two hydroxide ions. The formula for magnesium hydroxide is used to calculate the molar mass, density, and other physical properties of the substance. The formula also provides insight into the structure of the substance, as it indicates the number and types of atoms present in a molecule of magnesium hydroxide.
Magnesium Hydroxide Molar Mass
The molar mass of Mg(OH)2 is 58.32 g/mol. This is the mass of one mole of Mg(OH)2, which contains one mole of Mg atoms, and two moles of OH- ions. Molar mass is an important concept in chemistry because it is used to calculate the amount of substance in a given sample.
Magnesium Hydroxide Boiling Point
Mg(OH)2 does not have a distinct boiling point as it decomposes before reaching its boiling point. The decomposition temperature of Mg(OH)2 is around 350°C. When heated, Mg(OH)2 decomposes to form magnesium oxide and water.
Magnesium Hydroxide Melting Point
The melting point of Mg(OH)2 is 350°C. At this temperature, the solid Mg(OH)2 transitions to a liquid state. This process is known as melting. The melting point is an important physical property of a substance as it determines the temperature at which a solid changes to a liquid.
Magnesium Hydroxide Density g/mL
The density of Mg(OH)2 is approximately 2.36 g/mL. Density is defined as the mass of a substance per unit volume. Mg(OH)2 is a relatively dense substance due to its high molar mass and the presence of two OH- ions per Mg atom.
Magnesium Hydroxide Molecular Weight
The molecular weight of Mg(OH)2 is 58.32 g/mol. This is the sum of the atomic weights of all the atoms in one molecule of Mg(OH)2. Molecular weight is a useful concept in chemistry as it is used to determine the amount of a substance in a given sample.
Magnesium Hydroxide Structure
Mg(OH)2 has a layered structure consisting of Mg2+ ions and OH- ions. The Mg2+ ions are surrounded by six OH- ions, and the OH- ions are arranged in a hexagonal close-packed structure. The layered structure of Mg(OH)2 gives rise to its characteristic properties, such as its low solubility in water and its ability to form a suspension in water.
| Appearance | White powder or suspension |
| Specific Gravity | 2.36 g/mL |
| Color | White |
| Odor | Odorless |
| Molar Mass | 58.32 g/mol |
| Density | 2.36 g/mL |
| Melting Point | 350°C |
| Boiling Point | Decomposes at 350°C |
| Flash Point | Not applicable |
| Water Solubility | 12 mg/L at 20°C |
| Solubility | Insoluble in ethanol and ether |
| Vapor Pressure | Negligible |
| Vapor Density | Not applicable |
| pKa | 10.4 |
| pH | 10.5 |
Magnesium Hydroxide Safety and Hazards
Mg(OH)2 is generally considered safe to handle and use, with low toxicity and no known carcinogenic effects. However, prolonged exposure to Mg(OH)2 dust or powder may cause respiratory irritation and lung damage. Mg(OH)2 may also cause irritation or corrosion of the eyes, skin, and mucous membranes upon contact. It is important to follow proper safety precautions when handling Mg(OH)2, such as wearing protective equipment and working in a well-ventilated area. In case of contact or exposure, seek medical attention and rinse affected areas thoroughly with water.
| Hazard Symbols | None |
| Safety Description | – Avoid inhalation and contact with eyes, skin, and clothing. – Wear protective clothing, gloves, and eye/face protection. – Use in a well-ventilated area. |
| UN IDs | Not regulated |
| HS Code | 2826.90.90 |
| Hazard Class | Not classified |
| Packing Group | Not applicable |
| Toxicity | Low toxicity; prolonged exposure may cause respiratory irritation and lung damage. |
Magnesium Hydroxide Synthesis Methods
Various methods can synthesize Mg(OH)2, such as precipitation, hydrothermal synthesis, and electrochemical deposition.
The precipitation method involves reacting sodium hydroxide or ammonium hydroxide with magnesium chloride or magnesium sulfate to form Mg(OH)2. The reaction produces Mg(OH)2, which someone can collect and dry afterward.
To perform hydrothermal synthesis, one must heat water at high pressure and temperature while adding either magnesium oxide or magnesium carbonate. The process will produce Mg(OH)2, and you can collect the crystals by cooling the resulting solution.
An electrochemical deposition involves passing an electric current through a solution of magnesium ions, causing them to react with hydroxide ions and form Mg(OH)2 on the cathode.
Other methods of synthesizing Mg(OH)2 include the use of magnesium oxide and lime milk and the thermal decomposition of magnesium bicarbonate.
Each method has its advantages and disadvantages in terms of efficiency, yield, and cost. The choice of synthesis method depends on the specific application and desired properties of the Mg(OH)2 product.
Magnesium Hydroxide Uses
Mg(OH)2 has a wide range of applications in various industries, including:
- Antacid: Commonly used as an antacid to neutralize stomach acid and relieve heartburn, indigestion, and other digestive discomforts.
- Flame retardant: A non-toxic flame retardant used in plastics, rubber, and textiles to reduce the risk of fires.
- pH adjustment: Used to adjust the pH of various products, including water treatment solutions, cosmetics, and pharmaceuticals.
- Environmental remediation: Used in the treatment of wastewater and acid mine drainage to neutralize acidic conditions and remove heavy metals.
- Fertilizer: Used as a fertilizer to provide plants with magnesium and improve soil pH.
- Medical applications: Used as a laxative, and in certain medical procedures, such as colonoscopies, to clear the bowel.
- Other applications: Used as a stabilizer in latex paint, a whitening agent in paper, and a polishing agent in glass and ceramics.
Questions:
Q: What is a base used in toothpaste?
A: Mg(OH)2 is commonly used as a base in toothpaste to help neutralize acidic conditions in the mouth and reduce the risk of tooth decay.
Q: What is the formula for magnesium hydroxide?
A: The chemical formula for magnesium hydroxide is Mg(OH)2.
Q: Which chemical equation shows the dissociation of magnesium hydroxide?
A: The chemical equation for the dissociation of Mg(OH)2 is
Mg(OH)2 → Mg2+ + 2OH-.
Q: Is magnesium hydroxide soluble in water?
A: Mg(OH)2 is sparingly soluble in water, meaning it dissolves to a very limited extent.
Q: Which of the following substances is an Arrhenius acid? BF3, HCN, NH3, Mg(OH)2?
A: None of the substances listed are Arrhenius acids. BF3 and HCN are Lewis acids, NH3 is a weak Arrhenius base, and Mg(OH)2 is a strong Arrhenius base.
Q: Is Mg(OH)2 soluble in water?
A: Mg(OH)2 is sparingly soluble in water, meaning it dissolves to a very limited extent.
Q: What is the molar mass of Mg(OH)2?
A: The molar mass of Mg(OH)2 is approximately 58.32 g/mol.
Q: Is Mg(OH)2 an acid or base?
A: Mg(OH)2 is a base, as it is capable of accepting hydrogen ions (protons) to form water and a salt.