What is Stoichiometry?

Objectives:

6.0 Solve stoichiometric problems involving relationships among the number of particles, moles, and masses of reactants and products in

a chemical reaction 6.3 Identifying the nomenclature of ionic compounds, binary

compounds, and acids 6.4 Classifying chemical reactions as composition, decomposition,

single replacement, or double replacementOther AOD C.6.1 Define stoichiometry, reactants, and products.

Other AOD C.6.2 Explain the law of conservation of mass. Other AOD C.6.3 Explain the concept of mole in terms of Avogadro's

number.

Stoichiometry• Def.: the quantitative study of

relationships between amounts of reactants used and products formed in a chemical reaction

• Let’s think for a moment. If I hand you a dozen chocolate chips, can you make a dozen chocolate chip cookies?

• Well, every chemical equation is just a recipe!

Let’s Review!• Iron + oxygen react to produce iron (III)

oxide.1. Write AND BALANCE the chemical

equation. ANSWER: 4 Fe(s) + 3O2(g)→ 2Fe2O3(s)2. What type of reaction is this?3. How many moles of each compound are

represented?4. How many grams of each compound are

represented?

Review, continued…..• Aluminum + bromine react to produce

aluminum bromide1. Write AND BALANCE the chemical

equation. ANSWER: 2Al(s) + 3Br2(l)→ 2AlBr3(s)2. What type of reaction is this?3. How many moles of each compound are

represented?4. How many grams of each compound are

represented?

Review – 1 More!• Propane (C3H8) and oxygen react to

produce carbon dioxide and water.1. Write AND BALANCE the chemical

equation.ANSWER: C3H8(g) + 5O2(g)→ 3CO2(g) + 4H2O2. What type of reaction is this?3. How many moles of each compound are

represented?4. How many grams of each compound are

represented?

Law of Conservation of Mass• In every example, mass was conserved,

meaning the mass of the reactants EQUALS the mass of the products!

• While mass was equal on both sides of the equations, what was different?

ANSWER: number of molecules or number of moles

Assignment• Let’s look at Example Problem 12-1 on

p.355. (This is the last equation we balanced.)

• Notice how they write the equation “in terms of” molecules, moles, and mass.

• Now do the Practice Problems on p.356 ---- ONLY demonstrating conservation of mass, not the rest of the directions.

Mole Ratios• Def.: the ratio of the number of moles of

any two substances in a balanced chemical equation.

• Let’s look back at the 3 equations we balanced.

• In the first one, we can identify several mole ratios:– 4Fe/3O2 OR 3O2/4Fe– 4Fe/2Fe2O3 OR 2Fe2O3/4Fe– 3O2/2Fe2O3 OR 2Fe2O3/3O2

Mole Ratios, continued…..• What are the possible mole ratios for the

other two example problems we worked?

• Assignment: 1. Practice Problems (p.357)2. Study Guide for Content Mastery: pp.67-68