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Molar mass of sodium chloride

The molar mass of sodium chloride (NaCl) is 58.44 g/mol: the sum of the atomic weights 22.990 + 35.45. School problems round it to 58.5 g/mol (Na = 23, Cl = 35.5).

NaCl sodium chloride

Also called table salt

Molar mass

58.44 g/mol

For school problems (Na = 23, Cl = 35.5): 58.5 g/mol

Breakdown by element

M(NaCl) = 22.990 + 35.45 = 58.44 g/mol

The result is rounded to the precision of the least precise atomic weight. Atomic weights from IUPAC (CIAAW). Agrees with PubChem: 58.44 g/mol. PubChem CID 5234

What is sodium chloride?

Sodium chloride is table salt. In nature it occurs as the mineral halite (rock salt) and dissolved in seawater.

NaCl is made not of molecules but of Na⁺ and Cl⁻ ions in a 1 : 1 ratio, so its formula describes a formula unit. Its molar mass is worked out the same way as for molecules.

A 0.9% solution is used in medicine as normal saline. In industry, electrolysis of sodium chloride solution gives chlorine, hydrogen and sodium hydroxide.

Properties

State at 25 °C
Solid
Density
2.17 g/cm³ 25 °C
Melting point
800.7 °C
Boiling point
1413 °C other sources: 1465 °C
Solubility in water
soluble 36 g per 100 g of water, 25 °C

Sources: PubChem (HSDB, NIOSH), Wikipedia (CRC Handbook), NIST Chemistry WebBook; each value agrees in two of them.

Molar mass problems with sodium chloride

For school problems (Na = 23, Cl = 35.5): M(NaCl) = 58.5 g/mol

  1. Problem 1

    How many moles are in 175.5 g of NaCl?

    n = m ÷ M = 175.5 g ÷ 58.5 g/mol

    Answer: 3 mol

  2. Problem 2

    What is the mass of 4 mol of NaCl?

    m = n × M = 4 mol × 58.5 g/mol

    Answer: 234 g

  3. Problem 3

    What is the mass percentage of Na in NaCl?

    w(Na) = M(Na) ÷ M(NaCl) = 23 ÷ 58.5 ≈ 0.393

    Answer: 39.3%

  4. Problem 4

    How many Cl⁻ ions are in 0.1 mol of NaCl?

    N = n × NA = 0.1 mol × 6.02 × 10²³ mol⁻¹

    Answer: 6.02 × 10²²

What is molar mass?

Molar mass M is the mass of one mole of a substance, about 6.022 × 10²³ of its particles. It is measured in grams per mole (g/mol).

To find it, add up the atomic weights of all the atoms in the formula: multiply each element’s atomic weight by its subscript, the number of its atoms. In g/mol, the molar mass equals the relative molecular mass Mr.

For water: M(H₂O) = 2 × 1.0080 + 15.999 = 18.015 g/mol.