I. Balanced Equations Show Proportions

A. Relative Amounts in Equations Can be Expressed in Moles Stoichiometry -The branch of chemistry that deals with quantities (how much) of substances in chemical reactions

II. The Mole Ratio is the Key Used to convert the number of moles of one substance to a number of moles of another substance. A fraction made up from the COEFFICIENTS in a balanced equation *The mole ratio is the bridge connecting two different substances*

10 Na + 2 NaNO 3  6 Na 2 O + N 2 Moles of sodium : Moles of sodium oxide Moles of sodium nitrate : Moles of nitrogen 10 mol Na 6 mol Na 2 O 10 mol Na 2 mol NaNO 3 1 mol N 2 2 mol NaNO 3

2 Al(OH) H 2 SO 4  Al 2 (SO 4 ) H 2 O Moles of aluminum sulfate : Moles of sulfuric acid 3 mol H 2 SO 4 1 mol Al 2 (SO 4 ) 3 3 mol H 2 SO 4 Moles of water: Moles of aluminum hydroxide 6 mol H 2 O 2 mol Al(OH) 3 6 mol H 2 O

A. Using Mole Ratio as a conversion factor Four basic steps: 1 st Start out with a balanced chemical equation 2 nd Identify the known moles and unknown moles 3 rd Determine the mole ratio of the known and unknown 4 th Set up a conversion and solve for unknown moles

Stoichiometry is based on some assumptions: No side reactions Reaction goes to completion Reactants are completely consumed

Mole-Mole Conversion Factor Set Up ? mol known ? mol unknown Mole Ratio (balanced equation)

Example: How many moles of oxygen react when 4.5 moles of hydrogen burn to produce water? Step 1: Write a balanced equation. H 2 + O 2  H 2 O2 2

known = 4.5 mol H 2 unknown = ? mol O 2 Mole ratio: 1 mol O 2 2 mol H 2 Step 2: Identify the known and the unknown. Step 3: Determine the mole ratio.

Step 4: Set up the mole ratio as a conversion factor and solve for the unknown. 4.5 mol H 2 2 mol H 2 1 mol O mol O 2

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