Presentation on theme: "Limiting Reactants and Excess"— Presentation transcript:
1 Limiting Reactants and Excess What is the Limiting Reagent (Reactant)?It is the substance in a chemical reaction that runs out first.The limiting reactant (reagent) determines how much product you can make.If you are given amounts of more than one reactant, determine how much product you can make with each of them. Whichever produces the LEAST amount of product is your limiting reagent.
2 Practice ProblemsConsider the reaction:2 Al I2 2 AlI3Determine the limiting reagent of the product, aluminum iodide, if one starts with:a) moles of Al and 2.40 moles of iodineAlI2
3 Al is limiting reactant 1.20 moles of Al moles AlI moles AlI32 moles Al2.40 moles I moles AlI moles AlI33 moles I2Al is limiting reactant
4 What is the limiting Reactant with 1.20 grams of Al and 2.40 grams of iodine?A 1.20g AlB g I21.20 g Al 1mol Al mol AlI mols AlI3g 2 mol Al2.40 g I2 1 mol I mol AlI mols AlI3g 3 mole I2I2 is limiting Reactant! B
5 How many grams of excess reactant will remain? 2.40g I mol I mols Al gg 3 mole I mol Alg of Al reactedStarted with 1.20g g reacted1.03 g in excess
6 15.00 g aluminum sulfide and g of water react until the limiting reagent is used up. Here is the balanced equation for the reaction.Al2S H2O 2 Al(OH) H2Sa.) What is the maximum mass of H2S which can be formed from these reagents ?10.21g11.35 g15.00g Al2S mol Al2S mols H2S gg mol Al2S mol H2S10.21g H2S12.00g H2O 1 mol H2O mols H2S g18.008g mol H2O mol H2S11.35g H2SA g
7 What is the limiting Reactant? A . H2OB. Al2S3B!How much of the excess reactant is used up?A, gB gC g15.00g Al2S mol Al2S mols H2O gg mol Al2S mol H2010.84 g used up
8 Percent Yield Percent Yield = (Actual Yield / Theoretical Yield) * 100 Theoretical Yield is the amount that your stoichiometric calculations have predicted.Actual Yield is what you actually produced in an experiment.
9 Example: In the reaction between nitrogen gas and hydrogen gas producing ammonia: a.) If you start with 14 grams of N2 and 6.0 grams of H2, what will be the limiting reagent and the theoretical yield?b.) If 10. grams of the product was formed, what would be the percent yield?