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Chemistry Stoody Guide

Moles

  1. Convert between mass and moles of a sample
  2. Distinguish and convert between moles of atoms and molecules

Converting Between Mass and Moles

Moles: An arbitrary number of atoms () to help measurement’s / equations.

  • Mass of one mole of a given element is the atomic mass number in grams
  • Molar mass has the unit g/mol
  • Convert between mass and moles by setting up dimensional analysis. For example, to convert 5.0 g of Na to moles:

Distinguish Between Moles of Atoms and Molecules

  • Moles of atoms is the total number of different atoms. For example, the moles of atoms in 1 mole of NaCl is 1 mole of Na and 1 mole of Cl, or 2 moles.

[Advanced] Mole Fraction

Mole Fraction: The ratio of the number of moles of a component to the total number of moles in a mixture. For example, the mole fraction of NaCl in a solution of 1 mole of NaCl and 1 mole of H2O is:

For a mixture of 2 substances, A & B:

and