Unit: Stoichiometry Excess reactant calculations Day 5 - Notes
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 moles of iron with moles of oxygen? Word equation: Formula Equation: iron + oxygen iron (III) oxide Fe+O2O2 Fe 2 O Fe +3 O mol Fe 1 = mol Fe 2 O 3 2 mol Fe 2 O 3 4 mol Fe x mol O 2 1 = mol Fe 2 O 3 2 mol Fe 2 O 3 3 mol O 2 x Can be produced: K: molFe U: ? molFe 2 O 3 K: molO 2 U: ? molFe 2 O 3
Example: Limiting Reactant AND Excess Reactant Calculations a)What mass of CoCl 3 is formed from the reaction of 3.478x10 23 atoms Co with 57.92L of Cl 2 gas at STP? b)How much of the excess reactant reacts and how much is left over? 2Co + 3Cl 2 2CoCl x10 23 atomsCo 1 x 2 mol CoCl 3 2 mol Co = 95.40gCoCl 3 1 mol Co 6.02x10 23 atomsCo x gCoCl 3 1 mol CoCl 3 1Co= Cl= g 284.7gCoCl 3 x 57.92L Cl 2 1 x 2 mol CoCl 3 3 mol Cl 2 = 1 mol Cl L Cl 2 x gCoCl 3 1 mol CoCl 3 x LRER Can be produced: K: 3.478x10 23 atomsCo U: ? gCoCl 3 K: LCl 2 U: ? gCoCl 3
Example: Limiting Reactant AND Excess Reactant Calculations a)What mass of CoCl 3 is formed from the reaction of 3.478x10 23 atoms Co with 57.92L of Cl 2 gas at STP? b)How much of the excess reactant reacts and how much is left over? 2Co + 3Cl 2 2CoCl 3 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 L Cl x10 23 atomsCo 1 x 3 mol Cl 2 2 mol Co = 1 mol Co 6.02x10 23 atomsCo x 22.4L Cl 2 1 mol CoCl 3 x LRER K: 3.478x10 23 atomsCo U: ? L Cl 2 Reacts:
Example: Limiting Reactant AND Excess Reactant Calculations a)What mass of CoCl 3 is formed from the reaction of 3.478x10 23 atoms Co with 57.92L of Cl 2 gas at STP? b)How much of the excess reactant reacts and how much is left over? 2Co + 3Cl 2 2CoCl 3 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) L Cl 2 LRER 57.92L Cl L Cl 2 Left over:
Questions? Complete WS 5 for HOMEWORK!