Baby Stoich! (Ideal Stoichiometry)

1. Baby Stoich!(Ideal Stoichiometry) 10/19/10

2. stoichiometry = process of calculating the exact amount of products made from an exact amount of reactants, or vice-versa. “baby” stoich is stoichiometry where one of the reactants is available in an unlimited amount. In reality, this is not the case: one reactant will limit the amount of product that can be made, and the other one will be inexcess. for these problems, assume the other reactant is unlimited. stoichiometry uses two main components to do this: a correctly balanced, correctly written chemical equation a conversion table that converts not only units of a compound, but also converts one compound into another using a mole ratio. mole ratio = the ratio ofmoles of the compounds in a balanced chemical equation. This is shown by the coefficients in the equation. Ex: mole ratios: __mol C3H8 is required to make __ mol CO2. = __:__ __mol O2 is required to make __ mol H2O. = __:__ __mol H2O can be made from __ mol C3H8. = __:__ 3 1 5 4 __ C3H8 + __ O2 __ CO2 + __ H2O 3 1 3 1 4 5 4 5 4 1 4 1

3. as stated before, stoich problems rely on a conversion table that converts not only units of a compound, but also converts one compound (A) into another (B) using a mole ratio. this means you not only use the mole map like you did before, but you also start using both sides of the mole map side A is connected to side B with the mole ratio “bridge” “A” = your starting compound’s formula “B” = your desired compound’s formula so how does all this come together in a baby stoich problem? Let’s try one: Ex1: Iron (III) oxide reacts with sodium phosphate in a DR reaction. If you use 85.3g of iron (III) oxide, how many grams of iron (III) phosphate can you make? step 1: write and balance the chemical equation in the problem. __ ______ + __ _______  __ _______ + __ ______ 2 1 2 3 FePO4 Fe2O3 Na2O Na3PO4 2 4 6 4

4. Ex1: Iron (III) oxide reacts with sodium phosphate in a DR reaction. If you use 85.3g of iron (III) oxide, how many grams of iron (III) phosphate can you make? step 2: decide what pathway to take on the mole map from the A side to the Bside. Be sure to cross the mole ratio at some point. g Fe2O3 mol Fe2O3mol FePO4 g FePO4 (3 steps on the mole map) step 3: set up a conversion table and fill it in to convert from your starting number/unit/formula to your requested number/unit/formula. Insert coefficients from the balanced equation into the mole ratio. step 4: calculate, remembering that #s on the top multiply, and #s on the bottom divide. Now do you see why it’s important to write the formula after your unit? Number, Unit, Formula—In Every Step—ALWAYS! THIS IS THE MOLE RATIO!!! 1 Fe2O3 + 2 Na3PO42 FePO4+ 3 Na2O __ mol FePO4 2 1 mol Fe2O3 150.82 g FePO4 85.3 g Fe2O3 = 161.11 g FePO4 1 1 mol FePO4 159.70 g Fe2O3 __ mol Fe2O3 85.3159.7 2150.82 = 161.11

5. Ex2: How many liters of carbon dioxide can be produced if 78.94 g of octane combust? __ ______ + __ ___  __ _____ + __ _____ Ex3: How many grams of calcium borate are needed to react with aluminum thiosulfate to produce 4.35 x 1024 formula units of aluminum borate? __ ________ + __ ________  __ ________ + __ ________