STOICHIOMETRY Chapter 9

What is stoichiometry? Stoichiometry is the quantitative study of reactants and products in a chemical reaction. Another way of converting from one unit to another. A form of Dimensional Analysis.

What is a Mole? A mole is a number (or conversion unit) used to represent billions of small molecules or atoms. One mole is equal to Avagadros number. Avagadros number or (1 mole) = 6.02 x 1023 particles, molecules, or atoms Ex: 1 dozen = 12 eggs A ream = 500 sheets

How Big Is A Mole Video?

Mole Ratios A mole ratio converts moles of one compound in a balanced chemical equation into moles of another compound. The coefficients of a balanced equation indicates how many moles of a compound are present.

Mole Ratio Examples 1. 2Al2O3 (l) 4 Al (s) + 3O2 (g) Give the mole ratio of Al2O3 to oxygen (O2) 2H2 (g) + O2  2H2O (g) Give the mole ratio of Hydrogen to water.

Answers 1. 2:3 2. 2:2 (reduce) 1:1

Mole- Mole Problems Problems where the given unit is in moles and the unknown unit is in moles. OR Problems where the starting unit is in moles and the final unit is in moles.

Mole-to-Mole Problems (2) A can of butane lighter fluid contains 1.20 moles of butane (C4H10). Calculate the number of moles of carbon dioxide given off when this butane is burned. *Given unit is moles and unknown is moles. Therefore; this is a mole-to –mole conversion.

Mole-Mole Problems Step #1: Balance equation Step #2: Re-write the Given information 2C4H10 + 13O2 8CO2 + 10H2O 1.20 mol C4H10 X _________ Step #3: Fill in the Molar Ratios between two compounds 1.20 mol C4H10 X 8 mol CO2 (Reduce) = 4 mol CO2 2 mol C4H10. 1 mol C4H10 Step #4: Mulitply all the numbers on top and divide by all of the numbers on the bottom. Step #5: Write the answer 1.20 x 4 = 4.8 mol of CO2

Example 3.0 moles of magnesium combines with oxygen to form magnesium oxide. Calculate the number of moles of magnesium oxide produced. 2 Mg (s) + O2 (g) 2 MgO (s) Step #2: Re-write the Given 3.0 mol Mg X ________ Step #4: Fill in molar ratios for two compounds 3.0 mol Mg x 2 mol MgO = 6.0 mol MgO = 3.0 MgO 2 mol Mg 2.0 mol Mg

Class Assignment Complete Ch. 9 Wksht #1 (found on my website)

Converting Moles to Grams Problems where you are converting from moles( given unit) to mass (unknown unit). To convert from moles to grams: 1 mole of any substance is equal to its Molar Mass

Examples- Converting Moles to Grams Convert 5 moles of Al to grams: 5 moles of Al x 27.0 g of Al = 135 g of Al 1 mole of Al Convert 3 moles of NaBr to grams: 3 mol of NaBr x 102.9 g of NaBr = 308.7 g NaBr 1 mol of NaBr

Converting Grams to Moles Convert 5 grams of Al to moles: 5 g of Al x 1 mole of Al = .19 moles of Al 27.0 g of Al Convert 3 grams of NaBr to moles: 3 g of NaBr x 1 mol of NaBr = .03 mol of NaBr 102.9 g NaBr

Classwork / Homework Complete 9.2 Worksheet