Limiting Reagent and Percent Yield

Always start with the balanced equation N2(g) + 3H2(g) → 2NH3(g) The mole ratio is 1:3:2 If we have 1 mole of N2 and 6 moles of H2 what is the limiting reagent? What is the excess reagent?

Excess reagent – the reactant that is present in more that he required amount for a complete reaction Limiting reagent – the reactant that is completely consumed in a chemical reaction

To solve these problems use the mole bridge Remember: Only moles can cross Specifically only the original mole can cross And to cross you need to multiply or divide

You need a 1:1 comparison to decide who crosses! 0.75 mol of Iron react with 0.6 mol of oxygen to form iron(III)oxide. How many moles of iron(III)oxide form? 4Fe + 3O2 → 2Fe2O3 0.75 mol 0.60 mol X mol You need a 1:1 comparison to decide who crosses!

4Fe + 3O2 → 2Fe2O3 0.80 mol 0.60 mol X mol

4Fe + 3O2 → 2Fe2O3 0.85 mol 0.60 mol X mol

Percentage Yield Yield - the quantity of product produced in a chemical reaction IE what you get from the reaction

Two kinds of yield: Actual Yield: what is actually produced or what you can measure after the reaction Theoretical yield: the amount you calculate based on the balanced equation

Theoretical Yield 4Fe + 3O2 → 2Fe2O3 M = 56.85 g/mol 32.00 g/mol 159.69 g/mol 10.00 g 10.00 g Theoretical Yield?

Theoretical Yield 4Fe + 3O2 → 2Fe2O3 M = 56.85 g/mol 32.00 g/mol 159.69 g/mol 10.00 g 10.00 g Theoretical Yield = 14.05 g

Percentage Yield The theoretical yield for a reaction is 14.05 g and the actual Yield is 12.00 g. What is the %yield?

So what? Environment: Money Chemical waste Is connected to Poor yielding reactions Money