• Mass-mass calculations are the most practical of all mass-based stoichiometry problems.
  • Moles cannot be measured directly, while the mass of any substance can generally be easily measured in the lab.
  • The mass of the given substance is converted into moles by use of the molar mass of that substance from the periodic table.
  • The moles of the unknown are converted to mass by using the mole ratio from the balanced chemical equation.
  • Each answer has three significant figures, as shown below.
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