1. Melinda Cottrell Integrated Science Grade 10 Unit Conversions (Part 2)
Stoichiometry
Stoichiometry
Stoichiometry
Melinda Cottrell Integrated Science Grade 10 Unit Conversions (Part 2)

2. STOY-KEE-OM-E-TREE What is Stoichiometry?
A way to measure chemical quantities using chemical compound names and chemical equations
For example, if I needed to make exactly grams of calcium sulfate in lab, I could use stoichiometry to calculate how much of each reactant I would need.

3. The Chemical Equation Given this equation: N2(g) + 3 H2(g)  2NH3(g)
What are the “ingredients” of this equation?
What do you think the coefficients mean?
What does the (g) mean?

4. Interpreting the Equation
Stoichiometry allows you to interpret an equation several ways
The coefficients can mean
Particles
Moles
Mass
Volume

5. PRACTICE
Interpret this equation in terms of particles, moles, mass, and volume:
N2(g) + 3H2(g)  2NH3(g)
1. Particles = 1 molecule of N2 and 3 molecules of H2 yield 2 molecules of NH3 (NOTE: ≠ 2)
2. Moles = 1 mole of N2 and 3 moles of H2 yield 2 moles of NH3 (NOTE: ≠ 2)
3. Mass = 28.0 g of N2 and 6.0 g of H2 yields 34.0 g of NH3 (NOTE: mass of reactants WILL ALWAYS EQUAL mass of products = law of conservation of mass)
4. Volume = 22.4 L of N2 and 67.2 L of H2 yields 44.8 L of NH3 (NOTE: ≠ 44.8)

6. Calculations Using Stoichiometry
Mole to mole
Mass to mass
And any combination
Mole to mass
Particle to mole
Mass to volume

7. Just Use…
The Molar Road Map

8. PRACTICE: N2 + 3H2  NH3 Mole-mole calculations:
How many moles of ammonia are produced when 0.60 moles of diatomic nitrogen reacts with diatomic hydrogen? Click once for hint. Click again for answer.
STEP 1 = You are given 0.60 moles of N2 and must calculate moles of NH3
STEP 2 = From the molar map, you are going from moles of substance A to B (molar ratio is 1 N2 : 1 NH3)
STEP 3 = Set up your train tracks with two columns
STEP 4 = Round using correct significant figures
ANSWER: 0.60 mol of NH3

9. PRACTICE: LiOH + HBr  LiBr + H2O Mass-mass calculations:
Calculate the number of grams of lithium bromide given 5.40 grams of hydrobromic acid. Click once for hint. Click again for answer.
STEP ONE = You are given 5.40 g of HBr and must calculate LiBr
STEP TWO = From the molar map, you are going from grams of substance A to grams of substance B (1 HBr:1 LiBr molar ratio)
STEP THREE = Set up train tracks with 4 columns
STEP FOUR = Round using significant figures
ANSWER: 5.79 g LiBr

10. PRACTICE: C2H4 + 3O2  2CO2 + 2H2O Other calculations:
How many moles of carbon dioxide are produced from 45.0 grams of ethylene (C2H4)? Click once for hint. Click again for answer.
STEP ONE = You are given 45.0 g of C2H4 and must calculate moles of CO2
STEP TWO = From the molar map, you are going from mass of substance A to moles of substance B (1:2 molar ratio)
STEP THREE = Set up a 3 column train track
STEP FOUR = Round using significant figures
ANSWER: moles of CO2

11. Putting it All Together
Sodium chloride can be prepared by the combination reaction of sodium metal and chloride gas. How much (mass) of product is formed if 5.40 x 1023 molecules of chloride gas are used?

12. How Did You Do? 2Na + Cl2  2NaCl 104. 95 105 g NaCl
5.40 x 1023 molecule Cl2
1 mol Cl2
2 mol NaCl
58.5 g NaCl X
6.02 x 1023 molecule Cl2
1 mol NaCl