Is molar mass the same as relative formula mass?

They have the same number; relative formula mass has no units while molar mass is in g mol⁻¹.

How do I include water of crystallisation?

Add the mass of each water molecule — for CuSO₄·5H₂O, add 5 × 18 to the mass of CuSO₄.

ChemistryGCSE, IGCSE & A Level

Molar mass is the mass of one mole of a substance in grams, numerically equal to its relative formula mass.

Add the relative atomic masses of every atom in the formula, taking care with brackets and water of crystallisation.

Molar mass converts between the mass you can weigh in the lab and the moles you need for stoichiometry.

M_{r} = \dfrac{m}{n}

\mathrm{Ca(OH)_{2}}

40 + 2(16 + 1) = 74\,\text{g mol}^{-1}

Multiply everything inside a bracket by the subscript outside it — forgetting this on hydroxides and nitrates is a classic slip.

Is molar mass the same as relative formula mass?: They have the same number; relative formula mass has no units while molar mass is in g mol⁻¹.
How do I include water of crystallisation?: Add the mass of each water molecule — for CuSO₄·5H₂O, add 5 × 18 to the mass of CuSO₄.

A mole is the amount of substance containing 6.02 × 10²³ particles — the chemist's counting unit that links mass to number of particles.

Concentration is the amount of solute dissolved in a given volume of solution, usually in moles per cubic decimetre.

Take molar mass from a definition to full marks with exam-board question banks, revision notes and instant step-by-step feedback from Study Coach.

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