1. Chapter 9B Notes Stoichiometry
West Valley High School
General Chemistry
Mr. Mata

2. Grams -> grams Calculation
Steps:
1. Balance the chemical equation.
2. Write grams of given reactant/product.
3. Use molar mass to find mole/gram ratio.
4. Multiply by the mole/gram ratio:
given g A x mol A x mol B x g B = ___ g B
g A mol A mol B

3. Route to Calculating Mass Relationships
Insert figure 11.1

4. Example Problem #1 N2 + 3 H2 2NH3
How many grams of NH3 will be produced if you start with 50 grams of N2?
Grams A moles A moles B grams B
Grams N moles N moles NH grams NH3
Step 1: grams N mol N2
50 grams N2 x 1 mol N2 = 1.8 mol N2
28 grams N2

5. Example Problem #1 N2 + 3 H2 2NH3
How many grams of NH3 will be produced if you start with 50 grams of N2?
Grams N moles N moles NH grams NH3
Step 2: mol N mol NH3
1.8 mol N2 x 2 mol NH3 = 3.6 mol NH3
1 mol N2

6. Example Problem #1 N2 + 3 H2 2NH3
How many grams of NH3 will be produced if you start with 50 grams of N2?
grams N moles N moles NH grams NH3
Step 3: mol NH grams NH3
3.6 mol NH3 x 17 gram NH3 = 61.2 g NH3
1 mol NH3

7. Example Problem #2 N2 + 3 H2 2NH3
How many grams of NH3 will be produced if you start with 12 grams of H2?
grams H moles H moles NH grams NH3
Step 1: grams H mol H2
12 grams H2 x 1 mol H2 = 6 mol H2
2 grams H2

8. Example Problem #2 N2 + 3 H2 2NH3
How many grams of NH3 will be produced if you start with 12 grams of H2?
grams H moles H moles NH grams NH3
Step 2: mol H mol NH3
6 mol H2 x 2 mol NH3 = 4 mol NH3
3 mol H2

9. Example Problem #2 N2 + 3 H2 2NH3
How many grams of NH3 will be produced if you start with 12 grams of H2?
grams H moles H moles NH grams NH3
Step 3: mol NH grams NH3
4 mol NH3 x 17 grams NH3 = 68 grams NH3
1 mol NH3

10. Example Problem #3
__ KNO3 + __ Fe2O3 -> __ K2O + __ Fe(NO3)3
How many grams of K2O will be produced if you start with 80 grams of Fe2O3?
grams Fe2O moles Fe2O moles K2O g K2O
Step 1: grams Fe2O mol Fe2O3
80 grams Fe2O3 x 1 mol Fe2O = 0.5 mol Fe2O3
160 grams Fe2O3

11. Example Problem #3 Step 2: mol Fe2O3 mol K2O
6 KNO3 + Fe2O3 -> 3 K2O + 2 Fe(NO3)3
How many grams of K2O will be produced if you start with 80 grams of Fe2O3?
g Fe2O moles Fe2O moles K2O g K2O
Step 2: mol Fe2O mol K2O
0.5 mol Fe2O3 x 3 mol K2O = 1.5 mol K2O
1 mol Fe2O3

12. Example Problem #3 Step 3: mol K2O grams K2O
6 KNO3 + Fe2O3 -> 3 K2O + 2 Fe(NO3)3
How many grams of K2O will be produced if you start with 80 grams of Fe2O3?
g Fe2O moles Fe2O moles K2O K2O
Step 3: mol K2O grams K2O
1.5 mol K2O x 94 grams K2O = 141 g K2O
1 mol K2O

13. Chapter 9B SUTW Prompt
Describe the difference between solving a mole:mole and a mass:mass stoichiometry problem.
Complete a sentence paragraph using the SUTW paragraph format. Hilight using green, yellow, and pink.
Due Date: Monday, November 27th, 2017(start of class).