Limiting Reactants and Percent Yield Definitions The Limiting

Limiting Reactants and Percent Yield

Definitions • The Limiting Reactant is the reactant that limits the amounts of the other reactants that can combine and the amount of product that can form in a chemical reaction. • The excess reactant is the substance that is not used up in a reaction.

1 engine + 4 tires 1 car • If you have two engines and seven tires which is your limiting reactant and which is in excess? 2 engines 4 tires = 1 engine 8 tires

Practice problem#1 • Si. O 2 + 4 HF → Si. F 4 + 2 H 2 O • If 2. 0 moles of HF are exposed to 4. 5 moles of Si. O 2, which is the limiting factor? 2 mol HF 1 mole Si. O 2 4 moles HF = 0. 5 moles Si. O 2

Practice problems 2. N 2 H 4 + 2 H 2 O 2→ N 2 + 4 H 2 O a) Which is the limiting reactant in this reaction when. 750 moles of N 2 H 4 is mixed with. 500 mol of H 2 O 2? b) How much of the excess reactant, in moles, is left over?

Practice problems • Pg. 368 #’s 20 -21

Percent Yield • The theoretical yield is the maximum amount of product that can be produced from a given amount of reactant. (The result of a mass-mass problem) • The actual yield is the measured amount of a product obtained from a reaction.

When 36. 8 g of C 6 H 6 react with excess Cl 2, the actual yield of C 6 H 5 Cl is 38. 8 g. What is the percent yield of C 6 H 5 Cl? • C 6 H 6 + Cl 2 → C 6 H 5 Cl + HCl • Do a mass-mass problem to determine your theoretical yield. • Divide your actual yield by your theoretical yield and convert to percent. actual yield theoretical yield = 38. 8 g 53. 0 g =. 732 x 100 = 73. 2%