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Molar mass of magnesium chloride (MgCl₂)

The molar mass of magnesium chloride (MgCl₂) is 95.205 g/mol, summed from the IUPAC standard atomic weights of Mg, Cl x 2.

mol
Molar mass
95.205g/mol
= Exact Molar mass of magnesium chloride
Moles in the sample mass
0.105 036 5 mol
Mass of that amount of substance
95.205
Molecules in the sample mass
6.32545e+22
Show the working
  1. Mass of sample = 10
  2. Amount of substance = 1
  3. Molar mass = 24.305 + 35.45*2 = 95.205
  4. Moles in the sample mass = 10 / 95.205 = 0.105 037
  5. Mass of that amount of substance = 1 * 95.205 = 95.205
  6. Molecules in the sample mass = 0.105 037 * NA = 6.32545e+22

Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.

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    The formula

    • Molar mass = sum over elements of (atomic weight x number of atoms)
    • For MgCl₂: 24.305 + 35.45 x 2 = 95.205 g/mol
    • Moles = mass / molar mass; mass = moles x molar mass
    • Molecules = moles x 6.02214076 x 10^23 (the Avogadro constant, exact by definition)

    Molar mass in grams per mole is numerically equal to the molecular mass in daltons, so this figure doubles as the molecular weight.

    Atomic weights are the IUPAC 2021 standard values. Several elements have a range rather than a single value because isotope ratios vary between sources; the conventional single value is used here.

    Composition by mass

    Element Atoms Atomic weight Contribution (g/mol) Share of mass
    Chlorine (Cl) 235.4570.974.471 %
    Magnesium (Mg) 124.30524.30525.529 %

    Contributions add to the molar mass of 95.205 g/mol. Atomic weights are the IUPAC 2021 standard values.

    Frequently asked

    What is the molar mass of magnesium chloride?

    95.205 g/mol, for the formula MgCl₂.

    How do you convert grams of magnesium chloride to moles?

    Divide the mass in grams by 95.205 g/mol. One gram of magnesium chloride is 0.0105037 mol.

    How many grams are in one mole of magnesium chloride?

    95.205 g, by definition of the molar mass.

    Is molar mass the same as molecular weight?

    Numerically yes, for the purposes of this calculation. Molecular weight is a dimensionless ratio and molar mass carries units of g/mol, but the digits are identical.

    Where the numbers come from

    • IUPAC 2021 standard atomic weights; Avogadro constant fixed by the 2019 SI.

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