Magnesium hydroxide [Mg(OH)2] Molar Mass (With Calculations)

Magnesium hydroxide [Mg(OH)2] Molar Mass

Molar mass of Magnesium hydroxide [Mg(OH)2] is 58.319 g/mol.

Well, now you have come to know the molar mass of Mg(OH)2.

But how can you get this value?

Let me show you the calculation to get the molar mass of Mg(OH)2 (or Magnesium hydroxide).

If you are a visual learner like me, then here is a short one minute video for you.

Magnesium hydroxide [Mg(OH)2] Molar Mass Calculation

If you have a periodic table with you, then you can easily calculate the molar mass of Mg(OH)2 (or Magnesium hydroxide).

Because the molar mass of any molecule (or compound) can be calculated by simply adding the molar masses of individual atoms.

Now here we have to find the molar mass of Mg(OH)2 (or Magnesium hydroxide).

So for that, have a look at the periodic table given below.

You can see the molar mass value of all the atoms from this periodic table.

Now in Mg(OH)2, there are Magnesium atom, Oxygen atoms and Hydrogen atoms.

So let’s look at the molar mass of Magnesium, Oxygen and Hydrogen from the above periodic table.

You can see that;

The molar mass of Magnesium is 24.305 g/mol. [1]

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The molar mass of Oxygen is 15.999 g/mol. [2]

The molar mass of Hydrogen is 1.008 g/mol. [3]

Now, to calculate the molar mass of Mg(OH)2, you just have to add the molar mass of all the individual atoms that are present in Mg(OH)2.

So, Molar mass of Mg(OH)2 = (Molar mass of Magnesium atom) + (Molar mass of Oxygen atom + Molar mass of Hydrogen atom) × 2
= (24.305) + (15.999 + 1.008) × 2
= (24.305) + (17.007) × 2
= (24.305) + (34.014)
= 58.319 g/mol

Hence the Molar mass of Mg(OH)2 is 58.319 g/mol.

I hope you have understood the short and simple calculation for finding the molar mass of Mg(OH)2.


  • In some books, you may see the unit of molar mass as grams/mole or g/mole. But all these units (i.e g/mol, grams/mole and g/mole) are the same. 
  • Always follow the calculation order to avoid any mistakes in calculation. First solve the brackets, then multiplications and at last do the final addition.
  • And don’t forget to put the unit g/mol to your final calculated molar mass.

Check out other related topics for more practice;
KI (Potassium iodide) Molar Mass
NH4Cl (Ammonium chloride) Molar Mass
MgSO4 (Magnesium sulfate) Molar Mass
Benzene (C6H6) Molar Mass
KMnO4 (Potassium permanganate) Molar Mass


Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. With a desire to make learning accessible for everyone, he founded Knords Learning, an online learning platform that provides students with easily understandable explanations.

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