Basically stoichiometry is the measurement of elements, that is, the study of chemical quantities consumed or produced in a chemical reaction. When we are performing it we are using a special chemical counting unit: the mole, a unit of measurement, and one mole of a substance contains 6.022 * 10^23 particles. Now mole ratio is defined as the ratio of moles of one substance to the moles of another substance in a balanced equation. <span>If we are looking for the mole ratio between two substances, we need to look at the balanced equations</span> for the coefficients in front of the substances you are interested in. This should be your guiding mantra for doing stoichiometry problems!