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Reaction Stoichiometry. Objectives Understand the concept of stoichiometry. Be able to make mass-to-mass stoichiometric calculations.

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Presentation on theme: "Reaction Stoichiometry. Objectives Understand the concept of stoichiometry. Be able to make mass-to-mass stoichiometric calculations."— Presentation transcript:

1 Reaction Stoichiometry

2 Objectives Understand the concept of stoichiometry. Be able to make mass-to-mass stoichiometric calculations.

3 Stoichiometry stoichiometry: the process of calculating quantities involved in chemical reactions balanced chemical equations are required coefficients can represent the number of particles or the number of moles N 2 (g) + 3H 2 (g) → 2NH 3 (g) 1 mole 3 moles 2 moles mole ratio: ratio of moles involved in a reaction (using coefficients)

4 Stoichiometry Problem N 2 (g) + 3H 2 (g) → 2NH 3 (g) If 25.7 g of nitrogen gas completely reacts with an excess of hydrogen gas, what mass of ammonia is produced? # g N 2 → # mol N 2 → # mol NH 3 → #g NH 3 g A → mol A → mol B → g B A B A = what you know B = what you want This “pathway” is used in most stoichiometry problems

5 Stoichiometry Problem The process of smelting iron ore to iron can be carried out with the following reaction. How much ferric oxide is needed to produce 75.8 g of iron using this method? Fe 2 O 3 (s) + 3 CO(g) → 2 Fe(s) + 3 CO 2 (g)

6 Stoichiometry Problem A copper penny combines with oxygen in a crucible to form cuprous oxide. Write a balanced chemical equation for the reaction. What mass of oxygen is needed to completely react with a 3.12 g copper penny?

7 Objectives Understand the distinction between actual yield and theoretical yield. Be able to determine the percentage yield for a chemical reaction.

8 Percentage Yield theoretical yield: the maximum amount of product that can be produced (calculated using stoichiometry) actual yield: the actual amount of product produced in a chemical reaction The percent yield cannot exceed 100%

9 Percentage Yield Problem What is the percentage yield if 4.65 g of copper is produced when 1.87 g of aluminum reacts with excess cupric sulfate? 2 Al (s) + 3 CuSO 4 (aq) → Al 2 (SO 4 ) 3 (aq) + 3 Cu (s)

10 Objective You will be able to determine the limiting reagent (or reactant) for a chemical reaction when given the mass of two (or more) reactants.

11 Limiting Reagent limiting reagent: the reactant that is completely consumed first in a reaction (so it limits the amount of product) The reactant that yields the least product is the limiting reagent. Which substance is the limiting reagent if 3.50 g of sulfur reacts with 2.50 g of aluminum to produce Al 2 S 3 ? How much Al 2 S 3 is actually produced?


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