# Stoichiometry Chemistry II Chapter 9 Reaction Stoichiometry l

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Stoichiometry Chemistry II Chapter 9

Reaction Stoichiometry l Based on conservation of matter – l Balanced equation If the quantity of one substance is known, others can be found – Mole ratios

5 Step Process 1. 2. 3. 4. 5. Construct a balanced equation. Identify known(s) and unknown(s). Convert known(s) to moles (if necessary). Find moles of unknown(s). Convert unknown(s) into required units (if necessary).

Example Problem How many grams of nitrogen will react with 112 L of hydrogen to form ammonia (NH 3)?

Step One: Construct a Balanced Chemical Equation l l Nitrogen and hydrogen produce ammonia N 2 + H 2 NH 3 Be honest, did you forget the 2’s? N 2 + 3 H 2 2 NH 3

Step Two: Identify Known(s) and Unknown(s) l N 2 + 3 H 2 2 NH 3 ? g 112 L

Step Three: Convert Known to Moles l 112 L H 2 * 1 mol H 2 22. 4 L H 2 = ? mol H 2

Step Three: Convert Known(s) to Moles l 112 L H 2 * 1 mol H 2 = 22. 4 L H 2 5 mol H 2

Step Four: Find Moles of Unknown(s) l l Convert moles of known to moles of unknown. Use the mole ratio from the balanced equation.

Step Four: Find Moles of Unknown(s) l N 2 + 3 H 2 2 NH 3 l 5 mol H 2 * 1 mol N 2 3 mol H 2 = ? Mol N 2

Step Four: Find Moles of Unknown(s) l N 2 + 3 H 2 2 NH 3 l 5 mol H 2 * 1 mol N 2 3 mol H 2 = 1. 67 Mol N 2

Step Five: Convert Unknown(s) into Required Units l How many grams of nitrogen? l 1. 67 Mol N 2 * 28 g N 2 1 mol N 2 = ? g N 2

Step Five: Convert Unknown(s) into Required Units l How many grams of nitrogen? l 1. 67 Mol N 2 * 28 g N 2 1 mol N 2 = 46. 76 g N 2

Your Turn…. l 560 L of oxygen will react with hydrogen to make how many grams of water?

One: Construct a Balanced Chemical Equation l l l Oxygen and hydrogen produce water O 2 + H 2 O O 2 + 2 H 2 O

Two: Identify Known(s) and Unknown(s) l l O 2 560 L + 2 H 2 O ? g

Three: Convert Known(s) to Moles l 560 L O 2 * 1 mol O 2 22. 4 L O 2 = 25 mol O 2

Four: Find Moles of Unknown(s) l O 2 + 2 H 2 O l 25 mol O 2 * 2 mol H 2 O = 50 Mol H O 2 1 mol O 2

Five: Convert Unknown(s) into Required Units l 50 Mol H 2 O * 18 g H 2 O = 900 g H 2 O 1 mol H 2 O

The End? ?