Mathematics in Chemistry Stoichiometry Mathematics in Chemistry

Review: Calculations: 1 mole = 6.02 x 1023 molecules, form.units 1 mole = x grams, x is molar mass

Review: Molar Mass C10 H6 O3 TOTAL = 174.1 grams 10 C = 10 X 12.01g = 120.10 6 H = 6 X 1.00g = 6.00 3 O = 3 X 16.00g = 48.00 TOTAL = 174.1 grams

Review: Chemical Equations: Recipe for a Chemical Reaction Relative number of Reactant and Product CH4 + O2  CO2 + H2O

Review: Balancing Continued: C2H5OH (l) + 3O2 (g)  2CO2 (g) + 3H2O (g)

Basics of Stoichiometry Al + O2 → Al2O3 If the equation is not balanced, the first step is to balance the equation. 4 Al + 3 O2 → 2 Al2O3

Mole  Mole 4Al + 3O2 → 2Al2O3 How many moles of aluminum are in 6.40 moles of Aluminum Oxide? Step 1: Determine the ratio needed 4 mol Al or 2 mol Al2O3 2 mol Al2O3 4 mol Step 2: Set up the problem using dimensional analysis. 6.40 mol Al2O3 = 4 mol Al 12.80 mol Al 2 mol Al2O3 This is the Ratio determined in step 1

Mole  Mass 4Al + 3O2 → 2Al2O3 How many grams of aluminum are in 8.00 moles of oxygen? Step 1: Determine the ratio needed: 4 mol Al or 3 mol O2 3 mol O2 4 mol Al 8.00 mol O2 = g Al Steps: given – ratio – molar mass Step 2: Set up the problem 4 mole Al 26.98 g Al 287.79 3 mole O2 1 mole Al This is the Ratio determined in step 1

Mass  Mole 4Al + 3O2 → 2Al2O3 How many moles of oxygen are in 154.20 g of aluminum oxide? Step 1: Determine the ratio needed. 2 mol Al2O3 or 3 mol O2 3 mol O2 2 mol Al2O3 Step 2: Set up the problem 154.20 g Al2O3 = mol O2 Steps: given – molar mass - ratio This is the Ratio determined in step 1 1 mol Al2O3 3 mol O2 2.27 101.96 g Al2O3 2 mol Al2O3

Mass  Mass 4Al + 3O2 → 2Al2O3 How many grams of oxygen are in 54 g of aluminum? Step 1: Determine the ratio needed. 4 mol Al or 3 mol O2 3 mol O2 4 mol Al Step 2: Set up the problem Steps: Given – Molar Mass – Ratio – Molar Mass This is the Ratio determined in step 1 32 g O2 = 48.04 g O2 1 mol Al 3 mol O2 54 g Al 1 mol O2 26.98 g Al 4 mol Al