1. Unit: Stoichiometry Excess reactant calculations Day 5 - Notes

2. 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

3. 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: iron + oxygen  iron (III) oxide Fe+O2O2  Fe 2 O 3 32 4 Fe +3 O -2 13.17 mol Fe 1 = 6.585 mol Fe 2 O 3 2 mol Fe 2 O 3 4 mol Fe x 18.19 mol O 2 1 = 12.13 mol Fe 2 O 3 2 mol Fe 2 O 3 3 mol O 2 x Can be produced: K: 13.17 molFe U: ? molFe 2 O 3 K: 18.19 molO 2 U: ? molFe 2 O 3

4. 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 3.478x10 23 atomsCo 1 x 2 mol CoCl 3 2 mol Co = 95.40gCoCl 3 1 mol Co 6.02x10 23 atomsCo x 165.13gCoCl 3 1 mol CoCl 3 1Co=58.78 3Cl=106.35 165.13g 284.7gCoCl 3 x 57.92L Cl 2 1 x 2 mol CoCl 3 3 mol Cl 2 = 1 mol Cl 2 22.4L Cl 2 x 165.13gCoCl 3 1 mol CoCl 3 x LRER Can be produced: K: 3.478x10 23 atomsCo U: ? gCoCl 3 K: 57.92 LCl 2 U: ? gCoCl 3

5. 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. 19.41L Cl 2 3.478x10 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:

6. 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). 38.51L Cl 2 LRER 57.92L Cl 2 -19.41L Cl 2 Left over:

7. Questions? Complete WS 5 for HOMEWORK!