Limiting Reactant

Which will run out first? In the real world, one reactant will be consumed before other(s) In the real world, one reactant will be consumed before other(s) In these problems, each reactant’s amount will be provided, either in moles or mass In these problems, each reactant’s amount will be provided, either in moles or mass Two methods can be used Two methods can be used Trial Method Trial Method Advancement Method Advancement Method

Trial Method Use mass-mass stoichiometry calculation to determine how much Reactant B will be required to completely consume Reactant A. Use mass-mass stoichiometry calculation to determine how much Reactant B will be required to completely consume Reactant A. Sample Problem: 15.0g of N 2 reacts with 15.0g of H 2 to make ammonia according to the equation N 2 + 3H 2 → 2NH 3 Sample Problem: 15.0g of N 2 reacts with 15.0g of H 2 to make ammonia according to the equation N 2 + 3H 2 → 2NH 3 How much ammonia can be made? How much ammonia can be made?

Solution to Ex. 1 Trial method calculation Trial method calculation Trial method calculation Trial method calculation Advancement Method Advancement Method Moles of each reactant (n)/coefficient then compare results Moles of each reactant (n)/coefficient then compare results N 2 : 15.0g/28.02 g/mol /1mol = N 2 : 15.0g/28.02 g/mol /1mol = H 2 : 15.0g/2.016 g/mol /3mol = 2.48 H 2 : 15.0g/2.016 g/mol /3mol = 2.48 Which is the lowest value? Which is the lowest value? Lowest value is ALWAYS LR Lowest value is ALWAYS LR

And the point is… Since it runs out first, the limiting reactant must be calculated in order to determine the maximum theoretical yield for this reaction. Since it runs out first, the limiting reactant must be calculated in order to determine the maximum theoretical yield for this reaction. Assignment: Limiting Reactant Problem Set Assignment: Limiting Reactant Problem Set