1. Stoichiometry
Chapter 12

2. What is stoichiometry?
Calculations that deal with the amount of substances involved in chemical reactions.
Include both reactants and products

3. Calculation 1: Mole - Mole
Calculate the number of moles of one substance that will react or be produced by another substance with a given number of moles
Moles A  Moles B
Conversion Factor : Mole Ratio
Mole ratio comes from a BALANCED CHEMICAL EQUATION

4. Example: Mole - Mole CO2 + 2LiOH  Li2CO3 + H2O
How many moles of lithium hydroxide are needed to react with 20.0 moles of carbon dioxide?
K: mol CO2 UK: ? Mol LiOH
CF: 1 mol CO2 = 2 mol LiOH
ans. – 40.0 mol LiOH

5. Practice: Mole - Mole 2C2H6 + 7O2  4CO2 + 6H20
If 4.5 moles of ethane undergoes combustion, how many moles of oxygen are required?
Ans moles O2
If 7.36 moles of carbon dioxide are produced, how many moles of water are produced?
Ans moles H20

6. Calculation 2: Mass - Mass
Calculate the number of grams of one substance to react or be produced by a given number of grams of another substance.
THREE conversion factors
Mass A  Moles A  Moles B  Mass B
Conversion factors:
Molar mass of A
Mole ratio of A:B
Molar mass of B

7. Example: Mass - Mass Sn + 2HF  SnF2 + H2
How many grams of tin (II) fluoride are produced from a reaction containing 30.0 grams of hydrofluoric acid?
K: g HF UK: ? g SnF2
CF: 1 mol HF = g HF
2 mol HF = 1 mol SnF2
1 mol SnF2 = g SnF2
Ans g SnF2

8. Practice: Mass - Mass CaC2 + 2H2O  C2H2 + Ca(OH)2
How many grams of acetylene are produced by adding water to 5.00g of calcium carbide?
Ans. – 2.03 g C2H2
How many grams of water are needed to produce grams of calcium hydroxide?
Ans. – g H2O

9. Other: Practice
How many molecules of oxygen are produced from 29.2 grams of water as it decomposes?
H2O  H2 + O2
How many grams of nitrogen dioxide must react with water to produce 5.00 x 1022 molecules of nitrogen monoxide?
NO2 + H2O  HNO3 + NO

10. Other: Practice SO2 + O2  SO3
At STP, how many liters of oxygen are needed to produce 19.8 liters of sulfur trioxide gas?
At STP, how many liters of sulfur dioxide gas are needed to react with 15.4 liters of oxygen gas to produce sulfur trioxide?

11. Additional Practice Problems
15 mol
A. 51 g B. 101 g C mol
0.303 g
1.11 g
A. 1:21 B mol C. 970 kg
A mol B kg water; 33.0 kg carbon dioxide
A g B g
A mol B. 294 g
1:2 2; mg
3.3 mol
2:1 1:1; 360g
A. 38.1g B. 40.1g C mol
1:3 2:3 ; 81.0g
76.5 g; 12.5g