Chapter 7- Quantities in Chemical reactions (7.1) Stoichiometry-Part 1
Stoichiometry The information we can get from balanced chemical equations help us with our calculations of chemical reactions.
Stoichiometry of S’mores Imagine you are making the Perfect S’more You will need: 2 Graham Crackers 4 Chocolate Squares 1 Marshmallow
2 S’mores How many of each ingredient would you need to make 2 S’mores? 4 Graham Crackers 8 Chocolate Squares 2 Marshmallows
Stoichiometric Relationships The numerical relationship between the quantities of reacting substances that corresponds to the laws of stoichiometry. Stoichiometric relationships are expressed in whole numbers.
Types of Stoichiometric Relationships Particle : Particle Mole : Mole Mass : Mass
Particle : Particle Relationship The coefficient in a balanced chemical equation tells us how many atoms or molecules are involved. N2(g) + 3 H2(g) 2 NH3(g) 1 molecule 3 molecules 2 molecules Ex 1) If you want to produce 12 molecules of ammonia, how many molecules of nitrogen do you need?
Particle : Particle Relationship N2(g) + 3 H2(g) 2 NH3(g) 1 molecule 3 molecules 2 molecules Ex 2) If 30 molecules of hydrogen react, how many molecules of ammonia will be formed?
Mole : Mole Relationship The coefficients in a chemical equation can also represent moles. N2(g) + 3 H2(g) 2 NH3(g) 1 mole 3 moles 2 moles Ex 3) If 3.2 moles of hydrogen react, how many moles of ammonia will be produced?
C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g) Example 4 The balanced chemical equation for the combustion of propane is: C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g) a) How many mole of O2 are needed to react with 0.500 mol of C3H8? b) If 3.00 mol of C3H8 burn completely in O2, how many moles of CO2 are produced? c) How many molecules of O2 are needed to react with 2.00 mol of C3H8? Work out on board (remind students to write this down)
Example 4 – Answers a) n = 2.50 mol O2 b) n = 9.00 mol CO2 c) N = 6.02x1024 molecules O2
Homework Read 234-240 Textbook: p237 # 1-2 p238 # 4 – 7 (check answers on p273) P240 # 8-10