Unit: Stoichiometry Excess Reactant Calculations Day 5 - Notes Reaction on

After today you will be able to… Calculate the limiting reactant using other mole relationships Calculate how much of the excess reactant reacts and how much is left over

Other L.R. Calculations Example: How many moles of iron (III) oxide can be produced from the reaction of 13.17 moles of iron with 18.19 moles of oxygen? Word equation: Formula Equation: Fe+3 O-2 iron + oxygen  iron (III) oxide 4 Fe + 3 O2  2 Fe2O3 K: 13.17 molFe U: ? molFe2O3 Can be produced: 13.17 mol Fe 1 2 mol Fe2O3 4 mol Fe x 6.585 mol Fe2O3 = K: 18.19 molO2 U: ? molFe2O3 18.19 mol O2 1 2 mol Fe2O3 3 mol O2 x = 12.13 mol Fe2O3

Example: Limiting Reactant AND Excess Reactant Calculations What mass of CoCl3 is formed from the reaction of 3.478x1023 atoms Co with 57.92L of Cl2 gas at STP? How much of the excess reactant reacts and how much is left over? 2Co + 3Cl2  2CoCl3 1Co=58.78 3Cl=106.35 K: 3.478x1023 atomsCo 165.13g U: ? gCoCl3 LR 3.478x1023atomsCo 1 1 mol Co 6.02x1023atomsCo 2 mol CoCl3 2 mol Co 165.13gCoCl3 1 mol CoCl3 x x x = K: 57.92 LCl2 U: ? gCoCl3 Can be produced: 95.40gCoCl3 ER 57.92L Cl2 1 1 mol Cl2 22.4L Cl2 2 mol CoCl3 3 mol Cl2 x 165.13gCoCl3 1 mol CoCl3 x x = 284.7gCoCl3

Example: Limiting Reactant AND Excess Reactant Calculations What mass of CoCl3 is formed from the reaction of 3.478x1023 atoms Co with 57.92L of Cl2 gas at STP? How much of the excess reactant reacts and how much is left over? 2Co + 3Cl2  2CoCl3 To find out how much excess reactant reacts, do a third calculation using the limiting reactant as the known, and the excess reactant as the unknown. LR ER K: 3.478x1023atomsCo U: ? L Cl2 3.478x1023atomsCo 1 1 mol Co 6.02x1023atomsCo 3 mol Cl2 2 mol Co 22.4L Cl2 1 mol Cl2 x x x = Reacts: 19.41L Cl2

Example: Limiting Reactant AND Excess Reactant Calculations What mass of CoCl3 is formed from the reaction of 3.478x1023 atoms Co with 57.92L of Cl2 gas at STP? How much of the excess reactant reacts and how much is left over? 2Co + 3Cl2  2CoCl3 To find out how much is left over (unreacted), subtract the amount of the excess reactant that reacted from the original amount of excess reactant (from the problem). LR ER 57.92L Cl2 -19.41L Cl2 Left over: 38.51L Cl2

Questions? Begin WS5 Reaction on