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Molar mass is the mass of one mole of a substance, measured in g mol⁻¹. It connects mass, amount, and particle number in a conversion chain.

$n = m/M and m = nM$

To reach particles from mass, divide mass by molar mass to obtain moles, then use the Avogadro conversion and count the requested entities if the formula contains more than one.

Use units to choose the direction: 9.0 g of H₂O divided by 18.0 g mol⁻¹ gives 0.50 mol. To find molecules, continue from moles to nNₐ; do not multiply mass directly by the Avogadro constant.

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Calculate the number of hydrogen atoms in 1.00 g of propan-2-ol.

Retrieve the quantitative chain: count entities with mN_A, sum relative masses from formulae, convert mass with n=m/M, derive formula ratios, use n=VC for solutions, and apply gas-volume ratios at the same temperature and pressure.

Before finalising, check the requested entity, formula subscripts, units, dm³ conversion, balanced-equation coefficients, and any limiting reactant.

1.4.3—Molar mass (M)

Molar Mass Conversions

The Mole Summary

Solving Molar-Mass Problems