# Section 11.1 Defining Stoichiometry

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Section 11.1 Defining Stoichiometry
Describe the types of relationships indicated by a balanced chemical equation. reactant: the starting substance in a chemical reaction State the mole ratios from a balanced chemical equation. stoichiometry mole ratio The amount of each reactant present at the start of a chemical reaction determines how much product can form. Section 11-1

Composition Stoichiometry
Mass relationships of elements in compounds Example: Percent composition of hydrogen in water? Composition Stoichiometry

Particle and Mole Relationships
Why does a reaction stop? Reaction Stoichiometry is the study of quantitative relationships between the amounts of reactants used and amounts of products formed by a chemical reaction. Quantitative vs qualitative Section 11-1

Particle and Mole Relationships (cont.)
Stoichiometry is based on the law of conservation of mass. The mass of reactants must equal the mass of the products. Section 11-1

Section 11-1

Particle and Mole Relationships (cont.)
A ________________is a ratio between the numbers of moles of any two substances in a balanced equation. Section 11-1

Section 11.2 Stoichiometric Calculations
List the sequence of steps used in solving stoichiometric problems. chemical reaction: a process in which the atoms of one or more substances are rearranged to form different substances Solve stoichiometric problems. The solution to every stoichiometric problem requires a balanced chemical equation. Section 11-2

Using Stoichiometry All stoichiometric calculations begins with a balanced chemical equation. 4Fe(s) + 3O2(g)  2Fe2O3(s) Section 11-2

4 Types of Reaction Stoichiometry Problems
Mole – Mole (1 step) Mole – Mass (2 steps) Mass – Mole (2 steps) Mass – Mass (3 steps)

Mole Mountain (2) Section 11-2

Mole to Mole CO2 + Li(OH) → Li2CO3 + H2O
How many moles of Lithium hydroxide are required to react with 30 mol of carbon dioxide? Mole - Mole

3.00 mol of water to start. How many grams of glucose can be produced?
Mole to Mass CO H2O → C6H12O O2 3.00 mol of water to start. How many grams of glucose can be produced? Mole - Mass

Mass to Mole C + SO2 → CS2 + CO
If 8.00 grams of sulfur dioxide reacts, how many moles of carbon disulfide are produced? Mass - Mole

Mass to Mass Sn + HF → SnF2 + H2
How many grams of tin (II) fluoride are produced from reacting grams of HF? Mass - Mass

Section 11.3 Limiting Reactants
Identify the limiting reactant in a chemical equation. Identify the excess reactant, and calculate the amount remaining after the reaction is complete. Calculate the mass of a product when the amounts of more than one reactant are given. molar mass: the mass in grams of one mole of any pure substance Section 11-3

Section 11.3 Limiting Reactants (cont.)
excess reactant A chemical reaction stops when one of the reactants is used up. Section 11-3

The __________________________are all the leftover unused reactants.
Why do reactions stop? Reactions proceed until one of the reactants is used up and one is left in excess. The ______________________limits the extent of the reaction and, thereby, determines the amount of product formed. The __________________________are all the leftover unused reactants. Section 11-3

If I have 400 tires, 150 engines, 200 steering wheels, and 300 bucket seats (2 per car), how many complete cars could I make? What is the limiting reactant? What are the excess reactants?

Why do reactions stop? (cont.)
Determining the limiting reactant is important because the amount of the product formed depends on this reactant. Section 11-3

Calculating the Product when a Reactant is Limiting
S8(l) + 8Cl2(g) → 4S2Cl4(l) 200.0g S and 100.0g Cl2 Determine which is the limiting reactant Section 11-3

Calculating the Product when a Reactant is Limiting (cont.)
Using an excess reactant can speed up the reaction. Using an excess reactant can drive a reaction to completion. Section 11-3

Section Percent Yield Calculate the theoretical yield of a chemical reaction from data. process: a series of actions or operations Determine the percent yield for a chemical reaction. theoretical yield actual yield percent yield Percent yield is a measure of the efficiency of a chemical reaction. Section 11-4

Reactants stick to containers.
How much product? Laboratory reactions do not always produce the calculated amount of products. Reactants stick to containers. Competing reactions form other products. Section 11-4

How much product? (cont.)
The ___________________is the maximum amount of product that can be produced from a given amount of reactant. The ____________________is the amount of product actually produced when the chemical reaction is carried out in an experiment. Section 11-4

The percent yield of a product is the ratio of the actual yield expressed as a percent.

Percent Yield in the Marketplace
Percent yield is important in the cost effectiveness of many industrial manufacturing processes. If you are supposed to make 100 pounds of aspirin, and only produce 50 pounds, the company has now lost money. Section 11-4