Stoichiometry Introduction

Introduction to Stoichiometry Stoichiometry – study of the quantitative relationships between reactants and products in a chemical reaction. Mg(s) + 2 HCl(aq) → MgCl2 (aq) + H2 (g)

Mole Ratio 2 Al2O3(l) → 4 Al(s) + 3 O2 (g)

Mole Ratio How many moles of Aluminum can be produced from 13.0 moles of aluminum oxide?

Practice 2 Al2O3(l) → 4 Al(s) + 3 O2 (g) If 26.0 moles of aluminum are produced in a reaction, how many moles of oxygen will also be produced? How many moles of aluminum oxide are required to produce 18.1 moles of aluminum? If 23.0 moles of aluminum oxide react, how many grams of Aluminum will be produced?

Class Warmup Use the following reaction to answer the questions below. Iron (II) oxide reacts with oxygen gas to produce iron (III) oxide How many moles of oxygen gas are required to react with 2.4 moles of iron (II) oxide? How many grams of iron (III) oxide will be produced from 70.0 g of iron (II) oxide?

Class Warm-up In a thermite reaction, powdered aluminum reacts with iron (III) oxide to produce aluminum oxide and molten iron. What mass of aluminum oxide is produced when 2.3 g of aluminum reacts with iron (III) oxide? 2 Al + Fe2O3  2 Fe + Al2O3

Limiting Reactants Objective: Identify the limiting reactant in a chemical reaction Use the limiting reactant to calculate the maximum amount of product formed or the excess reactant in a reaction. Limiting Reactant – reactant that limits the amount of products that can form in a chemical reaction. Excess Reactant – substance that is not completely used up in a reaction

Limiting Reactants N2 + 3 H2  2 NH3

Which is the limiting reactant? For each of the following reactions and the given amount of reactants, determine the limiting reactant. Limiting Reactant 2 S + 3 O2  2 SO3 6 moles S ______ 10 moles O2 2 Na + 2 H2O  2 NaOH + H2 4 moles Na ______ 8 moles H2O Mg2Si + 4 H2O  2 Mg(OH)2 + SiH4 1 mole Mg2Si ______ 2 moles H2O

Finding the Limiting Reactant N2H4 (l) + 2 H2O2 (l)  N2 (g) + 4 H2O(l) Which is the limiting reactant when 0.750 mol of N2H4 is mixed with 0.500 mol of H2O2? A given amount of a reactant is used to determine the required amount of the other reactant. That amount is then compared to the actual amount.

Amount of product in a Limiting Reactant Problem What mass of barium nitride is produced from the reaction between 22.6 g barium and 4.2 g nitrogen gas?

Sample Problems When 2.6 g of hydrogen react with 10.2 g of oxygen, what mass of water will be produced? If 4.1 g of chromium is heated with 9.3 g of chlorine gas, what mass of chromium (III) chloride will be produced? What mass of sulfur dioxide is produced from the reaction between 31.5 g of S8 and 8.65 g of O2?

Finding the Limiting Reactant N2H4 (l) + 2 H2O2 (l)  N2 (g) + 4 H2O(l) How much of the excess reactant, in moles remains unchanged? How much of each product forms? 0.250 mol N2 & 1.00 mol H2O

Percent Yield Theoretical yield – maximum amount of product that can be produced as determined by a stoichiometric calculation and based on the law of conservation of matter Actual Yield-amount obtained in a reaction

Percent Yield Methanol can be produced through the reaction of CO and H2 in the presence of a catalyst. If 75.0 g of CO reacts to produce 68.4 g CH3OH, what is the percent yield?

Review 10.45 g of aluminum reacts with 66.55 g of copper (II) sulfate in a single replacement reaction. What is the limiting reactant? What is the mass of each product? What is the mass of the excess reactant leftover at the end of the reaction?