Summary
Highlights
Molecules are too small to see, yet they react in specific proportions (stoichiometry) by number, not mass. To bridge this gap, chemists use the mole, a huge number (Avogadro's number: 6.022 x 10^23) which allows us to quantify molecules in amounts that can be observed and measured in grams.
The mole serves as a conversion factor between atomic mass units (AMU) and grams. For instance, if one carbon atom weighs 12 AMU, then a mole of carbon atoms weighs 12 grams. Molar mass is the molecular mass expressed in grams. To find the molar mass of a substance, you simply sum the atomic masses of all atoms in the molecule from the periodic table.
The mole is essential for stoichiometric calculations, allowing chemists to predict reaction outcomes. To calculate the mass of a product from a given mass of a reactant, convert the initial mass to moles using molar mass, then apply the stoichiometric ratio from the balanced equation to find the moles of the product, and finally convert these moles back to grams using the product's molar mass. This multi-step conversion can be performed in a single calculation by arranging conversion factors.