Relative molecular mass
Relative molecular mass
Formula
Mr = Σ(Ar × number of atoms)
Real World
Pharmaceutical companies like Pfizer calculate the Mr of aspirin (C₉H₈O₄, Mr = 180) precisely when scaling up tablet production to ensure the correct molar dose of active ingredient per pill.
Exam Focus
For ionic compounds use 'relative formula mass', not molecular mass — examiners penalise incorrect terminology.
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