# Stoichiometry Stoichiometry comes from the Greek

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Stoichiometry Stoichiometry comes from the Greek
Unit 6 Stoichiometry comes from the Greek Words stoicheion, meaning “element,” And metron, meaning “measure.”

Introduction to Stoichiometry Day 1
Composition Stoichiometry deals with the mass relationships of elements in compounds. Reaction Stoichiometry involves the mass relationships between reactants and products in a chemical reaction. All reaction Stoichiometry calculations start with a balanced chemical equation. This equation gives the relative numbers of moles of reactants and products.

Reaction-Stoichiometry Problems
Reaction-Stoichiometry problems can be classified according to the information given in the problem and the information you are expected to find, the unknown. The given and the unknown may both be reactants, they may both be products, or one may be a reactant and the other a product! The masses are generally expressed in grams. Stoichiometric problems are solved by using ratios from the balanced equation to convert the given quantity.

Given and unknown quantities are amounts in moles.
Problem Type 1 Given and unknown quantities are amounts in moles. Road Map…

Problem Type 2 Given is an amount in moles and the unknown is a mass that is often expressed in grams. Road Map…

Given is a mass in grams and the unknown is an amount in moles.
Problem Type 3 Given is a mass in grams and the unknown is an amount in moles. Road Map…

Given is a mass in grams and the unknown is a mass in moles.
Problem Type 4 Given is a mass in grams and the unknown is a mass in moles. Road Map…

Mole Ratio Solving any reaction-stoichiometry problem requires the use of a mole ratio to convert from moles or grams of one substance in a reaction to moles or grams of another substance. A mole ratio is a conversion factor that relates the amounts in moles of any two substances involved in a chemical reaction. This information is obtained directly from the balanced chemical equation.

List all the possible ratios you can obtain from the following balanced equation…there are 6

To determine the amount in moles of aluminum that can be produced from 13.0 mol of aluminum oxide, the mole ratio needed is that of Al to Al₂O₃. Mole ratios are exact, so they do not limit the number of significant figures in a calculation. The number of significant figures in the answer is therefore determined only by the number of significant figures of any measured quantities in a particular problem.

Molar Mass Recall that the molar mass is the mass, in grams, of one mole a substance. You will need to determine molar masses using the periodic table. For Example:

What are all of the possible conversion factors that can be expressed using these molar masses?

To find the number of grams of aluminum equivalent to 26
To find the number of grams of aluminum equivalent to 26.0 mol of aluminum, the calculation would be as follows.

Lets Practice! For each of the following chemical equations, write all possible mole ratios…
2HgO(s)→2Hg(l)+O₂(g) 4NH₃(g)+6NO(g)→5N₂(g)+6H₂O(l)

Creating your Project You will produce a multi-media file using SmartBoard software and your choice of technology to create a presentation of the 4 types of reaction-stoichiometry problems. You are allowed to choose four of the problems from the sample problem sheet to use in your project. You must include video and voice while describing how to problem solve each of the four types of problems. Eye candy is important and you may work in pairs of two. Finished projects must be uploaded to the SchoolWeb site by the end of class and be titled by students first names.

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