• Stoichiometry – Multi Step Conversions

• Stoichiometry is the calculation of quantities in chemical reactions.
• When you know the quantity of one substance in a reaction, you can calculate the quantity of another substance consumed or created in the reaction.
• A quantity can be grams, moles, liters, molecules, atoms, ions, formula units or particles.
• Theoretical yield is the maximum amount of product that will form during a reaction. (how much you expect to make)
• Example: 1 box of muffin mix says it will make 12 muffins
• Any time you are calculating the amount of product produced you are calculating theoretical yield.
• Actual yield is the amount of product that actually forms when the reaction is carried out in a laboratory.
• Example: when used the 1 box of muffin mix only makes 11 muffins (instead of the 12 it theoretically should have made).

• Stoichiometry Calculations General Steps
• The first step is to convert the give substance measurement to moles. (if not starting with moles)
• Next use the mole ratio to switch between substances
• Finally convert to the desired substance to the correct unit for the final answer.
• Remember:
• 1 mol = (molar mass) grams
• RECAL: molar mass is the SUM of ATOMIC MASSES
• 1 mol = 22.4 Liters
• 1 mol = 6.02 x 1023 particles (ptl)
• _____ mol A = ____ mole B     [called the mole ratio]
• These are the ONLY conversion you can do.
• Things to remember
• Don’t let the words in the problem confuse you. If it doesn’t have a number or a unit it probably is not important.  Especially when given the complete chemical equation.
• You MUST have a balanced chemical equation to do ANY mole to mole conversions.
• The coefficients in the balanced chemical reaction are used in the mole ratio ONLY
• Mole ratios are the ONLY place that you can switch substances.
• Can NOT do this [], you can only go from gram to mole, volume to mole, particles to mole
• The starting amount (# given in the problem) is only written ONE time, and never in a conversion fraction.
• Any time you have a reactant in excess it does NOT affect calculations (you can ignore it)
• Some students find using the mole map helpful 