Molar Mass of Mg(OH)2 (Magnesium Hydroxide)

Molar Mass Calculator

What is the molar mass of Mg(OH)₂?

Answer

M(Mg(OH)₂) =

58.319 g/mol

Atomic weights: IUPAC standard values (CIAAW, 2024).

Mg(OH)₂ = Mg + 2 × (O + H) → Mg 1, O 2, H 2

Contribution of each element
Element	Atoms, n	Atomic weight, A	n × A, g/mol Mass fraction, w	Mass fraction, w
Mgmagnesium	1	24.305	24.305 w ≈ 41.68%	≈ 41.68%
Ooxygen	2	15.999	31.998 w ≈ 54.87%	≈ 54.87%
Hhydrogen	2	1.0080	2.0160 w ≈ 3.46%	≈ 3.46%
Σ = 58.319 g/mol w = 100%				100%

Each fraction is rounded on its own, so the printed ones add up to 100.01%; unrounded, they make exactly 100%.

Atomic weights: CIAAW, Abridged Standard Atomic Weights (2024)

Mass fractions of the elements

O 54.87%Mg 41.68%

H 3.46%

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Molar masses of substances nearby

Formula	M, g/mol
C₃H₆O (acetone)	58.080
KF (potassium fluoride)	58.096
C₄H₁₀ (butane)	58.124
Mg(OH)₂ (magnesium hydroxide)	58.319
NaCl (sodium chloride)	58.44
Ni (nickel)	58.693
Co (cobalt)	58.933

FAQ

What is the molar mass of Mg(OH)2?

M(Mg(OH)₂) = 58.319 g/mol

How to calculate the molar mass of Mg(OH)₂?

Add up the atomic weights of all the atoms in the formula: 24.305 + 2 × 15.999 + 2 × 1.0080 = 58.319 g/mol.

How many grams are in 2 moles of Mg(OH)₂?

m = n × M = 2 mol × 58.319 g/mol = 116.638 g.

See Also