Mr. Orlando’s SCH3U/4C
Lesson 3.5 - Stoichiometry
3.5 – Stoichiometry
November 7, 2023
“S – toy – key – ah – met – ree”
Stoichiometry is the RATIO of atoms of each element involved in a chemical reaction. For example:
H2O(l)

H2(g) +
In this reaction,
water molecules decompose, forming
oxygen molecules. We can then define the following
O2(g)
hydrogen molecules and
STOICHIOMETRIC RATIOS:
N.B. 1: It does not matter which element is in the numerator and which is in the denominator. You may
flip the fractions at will.
These stoichiometric ratios can be used with dimensional analysis to determine the outcomes of
chemical reactions.
E.G. 1: How many moles of hydrogen gas are produced when 2.3x10-3 mol of water
decompose?
Mr. Orlando’s SCH3U/4C
Lesson 3.5 - Stoichiometry
November 7, 2023
E.G. 2: How many moles of oxygen gas are produced if 3.4x103 grams of lithium oxide are
decomposed?
E.G. 3: If 3.2 g of solid copper were to react with excess oxygen, how many grams of metal
oxide would be produced?
Mr. Orlando’s SCH3U/4C
Lesson 3.5 - Stoichiometry
November 7, 2023
E.g 4: If 3.7g of ethane (C2H6) combust completely, what mass of CO2 and H20 are
produced?
E.g. 5: What is the mass of solid product when 4.5x10-3g of magnesium react with excess
chlorine gas.
Mr. Orlando’s SCH3U/4C
Lesson 3.5 - Stoichiometry
November 7, 2023
E.g. 6: When 1.5g of lithium reacts with excess copper (2) sulfate, what mass of solid copper
is produced?
E.g. 7: When 4.4g of calcium nitrate reacts with excess lithium sulfate, what is the mass of
the precipitate produced?