Chemistry Formulas

Magnesium Hydroxide Formula

Magnesium Hydroxide is said to be an inorganic base that is not toxic in nature. In fact, we refer to its aqueous suspension as milk of magnesia which is a pretty common antacid. Learn magnesium hydroxide formula here.

Formula and Structure             

When we talk about the chemical formula for Magnesium Hydroxide, we see that it is Mg(OH)2. Moreover, the molar mass of the same is said to be 58.32 g/mol. We will discuss the chemical structure of Magnesium Hydroxide through the help of the image given below. Moreover, the central Mg is bonded to the 2 hydroxyl groups. The compound majorly exists as Mg2+ and OH- ions as it is ionic.

magnesium hydroxide formula


You can find Magnesium Hydroxide naturally. It is present in nature in the form of the mineral Brucite. Further, it is a chief source of Mg(OH)2 for various applications.


It has application in many fields. When we talk about the industrial applications of Magnesium Hydroxide, we see that we extract is from seawater. This is so because Mg salts are usually found in seawater. Moreover, Magnesium chloride which is present in seawater that reacts with lime i.e. Calcium Oxide to produce the Mg2+ and OH- ions that precipitate into Magnesium Hydroxide salt.

After that, we see there we can also opt for some other method to obtain Mg(OH)2. It is through the method of electrolysis of fused Magnesium Chloride. When we talk about it as Brucite, we see that it can be produced by the alkali-carbonate reaction where the Magnesium Carbonate is reacted with Alkali Hydroxides like KOH and NaOH.

MgCO3 + 2 NaOH → Mg(OH)2 + Na2CO3

Physical Properties

We see that Magnesium Hydroxide is present in a white solid form which is odourless. It has a density of 2.34 g/mL. Moreover, when we talk about its melting point, we see that it is 350 °C. Further, you will notice that it is also present as an aqueous suspension in water.

Chemical Properties

When present at very high temperatures, we see that the solid Magnesium Hydroxide experiences quite an endothermic decomposition i.e. it absorbs heat from the atmosphere.  It decomposes into Magnesium Oxide and water which is what makes it a good smoke suppressing and fire-fighting agent.

Mg(OH)2 → MgO + H2O

One can say that it is moderately basic which helps it in neutralizing mild acids. Moreover, it has an active disassociation in water to give hydroxyl ions and Mg ions. Further, we see that it is soluble in water, however, as it readily disassociates, it produces a white milky suspension. This is why it has the name of milk of magnesia.


As the nature of Magnesium Hydroxide is slightly basic as well as not toxic, it has a common use an antacid. Thus, as an antacid, it plays the role of neutralizing stomach acids and preventing indigestion and heartburn. Moreover, we can also use it in the form of underarm deodorant, laxative, antiperspirant, treatment of sores, in the treatment of wastewater, and also as a fire retardant.

Safety Hazards

Therefore, after looking at the above physical and chemical properties as well as the uses of it, it is safe to say that it is not lethal or harmful in nature. On the other hand, it is said to be fit for use by human beings but only in commended quantities.

Solved Question on Magnesium Hydroxide Formula

Question- What is the chemical formula for Magnesium Hydroxide?

a) MoG2

b) Mg(OH)2

c) MgH2

d) MgO

Answer- The correct answer is option B.

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