# Stoichiometry Introduction.

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Stoichiometry Introduction

Introduction to Stoichiometry
Stoichiometry – study of the mass 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?

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?

Finding the Limiting Reactant
N2H4 (l) + 2 H2O2 (l)  N2 (g) + 4 H2O(l) Which is the limiting reactant when mol of N2H4 is mixed with 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.

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? mol N2 & 1.00 mol H2O

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?

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?