Stoichiometry

Past paper questions, key definitions, and mark schemes — all files verified from our archive.

• Relative atomic mass (Ar): average mass of atom relative to C-12
• Relative molecular mass (Mr): sum of Ar in a molecule
• Mole: amount of substance containing 6.02×10²³ particles
• Moles = mass / molar mass (n = m/M)
• Moles = concentration × volume (n = cV) for solutions
• Moles = volume / 24 (at RTP, for gases in dm³)
• Empirical formula: simplest whole number ratio of atoms
• Molecular formula: actual number of atoms in a molecule

+ more definitions available in the full revision notes

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