## Stoichiometry

**Housekeeping:**Welcome back! I hope you guys had a great holiday. We are going to spend the next few weeks on stoichiometry. Stoichiometry is a method that uses relationships between reactants and products in a chemical reaction to determine desired quantitative data.

Before we get into stoichiometry, we need to introduce the concept of the mole.

**Mission 1: The Mole**

Mission Objectives. By the end of this lesson, you should be able to:

Mission Objectives. By the end of this lesson, you should be able to:

1. Define the "mole."

2. Calculate the molar mass of a compound.

3. Solve simple mole conversion problems.

**Content Review:**

Text: Chapters

Links: Chemical Equations The Mole

**NOTICE:**YOU WILL NEED YOUR CALCULATORS AND PERIODIC TABLES FOR THIS UNIT.

The mole is the SI unit for counting particles. One mole of any substance contains 6.02 * 10^23 particles. This number is known as Avogadro's Number, named after Italian scientist Amedeo Avogadro.

"Particles" is a generic term for atoms, formula units, and molecules. Avogadro's number of atoms clearly references an element, Avogadro's number of formula units references an ionic compound, and Avogadro's number of molecules references a covalent compound.

The molar mass of a substance is either the element's atomic mass on the periodic table, or the sum of the atomic masses of a formula unit or a compound.

For example: Hydrogen's molar mass is 1.01 g/mol. But water, which is H2O, is 18.02 g/mol. The 18.02 comes from adding the two hydrogens (2.02) with oxygen (rounded up to 16.00). So whenever you are dealing with the molar mass of a compound, you must add up the atomic mass of all of the atoms in that compound.

We will practice. Get comfortable with this process, as it is significant for solving stoichiometric problems.

Download these practice problems.

1. Molar Mass 2. Mole Conversions (I) 3. Mole Conversions (II)

Sample mole conversion problems:

1) How many moles are in 25 grams of water?

2) How many grams are in 4.5 moles of Li2O?

3) How many molecules are in 23 moles of oxygen?

4) How many moles are in 3.4 x 10^23 molecules of H2SO4?

5) How many molecules are in 25 grams of NH3?

6) How many grams are in 8.2 x 10^22 molecules of N2I6?

Let's Practice!

For example: Hydrogen's molar mass is 1.01 g/mol. But water, which is H2O, is 18.02 g/mol. The 18.02 comes from adding the two hydrogens (2.02) with oxygen (rounded up to 16.00). So whenever you are dealing with the molar mass of a compound, you must add up the atomic mass of all of the atoms in that compound.

We will practice. Get comfortable with this process, as it is significant for solving stoichiometric problems.

Download these practice problems.

1. Molar Mass 2. Mole Conversions (I) 3. Mole Conversions (II)

Sample mole conversion problems:

1) How many moles are in 25 grams of water?

2) How many grams are in 4.5 moles of Li2O?

3) How many molecules are in 23 moles of oxygen?

4) How many moles are in 3.4 x 10^23 molecules of H2SO4?

5) How many molecules are in 25 grams of NH3?

6) How many grams are in 8.2 x 10^22 molecules of N2I6?

Let's Practice!

**Mission 2: Real Chemistry**

Mission Objectives. You should be able to...

Mission Objectives. You should be able to...

1. Observe and describe the reactants and products of a chemical reaction.

Everything that we did last semester was building to this. You now know how to write and balance a chemical equation. What you will do with it is derive the molar quantitative outcomes, given a certain amount of reactants. Then you will complete a simple experiment using this information.

Practice Problems

The next activity you will do is a formal lab where you perform some basic stoichiometry and complete the calculations. Your group will write up the entire lab and submit it on a given date. This will be graded under Criterion B and C.