This episode introduces stoichiometry, the calculation of quantities in chemical reactions. This is part 1 in a 3 episode series. This first episode explains that the mole ratios from a balanced chemical equation are the key to all calculations. Using dimensional analysis, it demonstrates how to perform mole-to-mole conversions, emphasizing that unit cancellation ensures the correct setup. It works through several examples and also shows how to work backward from a desired product amount to find the necessary reactant quantity. The episode concludes with a review of common mistakes, reinforcing the importance of using a balanced equation and setting up mole ratios correctly.