1. Stoichiometry NC Essential Standard 2.2.4
Stoichiometry NC Essential Standard Analyze the stoichiometric relationships inherent in a chemical reaction
Stoichiometry
NC Essential Standard
2.2.4
Analyze the stoichiometric relationships inherent in a chemical reaction

2. STOICHIOMETRY
Get a pencil, paper, calculator and a periodic table and let’s get to work.
Get a pencil, paper, calculator and a periodic table and let’s get to work.

3. Use the molar mass to convert grams to moles.
Review: Converting grams to moles.
Determine how many moles there are in 5.17 grams of Fe(C5H5)2.
Given
Goal
5.17 g Fe(C5H5)2
= moles Fe(C5H5)2
0.0278
Use the molar mass to convert grams to moles.
Fe(C5H5)2
A quick review of converting grams to moles. This is how to determine how many moles there are in 5.17 grams of ferrocene, Fe(C5H5)2. First calculate the molar mass. This will be used as a conversion factor to convert grams to moles. Write down your given. Then draw your box. Write the molar mass at the bottom right and the 1 mole above it. Cancel like units top to bottom left to right. Multiply across the top and bottom then divide bottom into the top.
2 x 5 x =
2 x 5 x =
1 x = +

4. Use the molar mass to convert moles to grams.
Review: Converting moles to grams.
Determine how many grams are in 1.5 moles of Fe(C5H5)2.
Given
Goal
1.5 moles Fe(C5H5)2
g Fe(C5H5)2
= g Fe(C5H5)2
278.96
1 mole Fe(C5H5)2
Use the molar mass to convert moles to grams.
Fe(C5H5)2
A quick review of converting moles to grams. This is how to determine how many moles there are in 1.5 moles of ferrocene, Fe(C5H5)2. First calculate the molar mass. This will be used as a conversion factor to convert moles to grams. Write down your given. Then draw your box. Write 1 mole at the bottom right and the molar mass above it. Cancel like units top to bottom left to right. Multiply across the top and bottom then divide bottom into the top.
2 x 5 x =
2 x 5 x =
1 x = +

5. coefficients give MOLAR RATIOS
Stoichiometry Uses Mole Ratios
Ratios are found within a chemical equation.
2HCl + Ba(OH)2  2H2O BaCl2 1 1
coefficients give MOLAR RATIOS
2 moles of HCl react with 1 mole of Ba(OH)2 to form 2 moles of H2O and 1 mole of BaCl2
Stoichiometry uses mole ratios from the balanced equation. Ratios are formed from the coefficients in a balanced chemical equation. You can make mole ratios out of any combination of coefficients and formulas. The examples here are just a few of the possible mole ratios.
You can make mole ratios out of any combination of coefficients and formulas. The examples here are just a few
2mol HCl
1mol Ba(OH)2
2mol HCl
2mol H2 O

6. (1-2-3) General Approach For Problem Solving:
1. Clearly identify the Goal or Goals and the UNITS involved. (What are you trying to do?)
2. Determine what is given and the UNITS.
This is a (1-2-3) General Approach For Problem Solving. 1. Clearly identify the Goal or Goals and the UNITS involved. (What are you trying to do?) 2. Determine what is given and the UNITS Use conversion factors (which are really ratios) and their UNITS to CONVERT what is given into what is desired.
3. Use conversion factors (which are really ratios) and their UNITS to CONVERT what is given into what is desired.

7. Sample problem for setting up a stoichiometric problem.
Sam has entered into a 10 mile marathon. Use ALL of the following conversions (ratios) to determine how many inches there are in the race.
5280 ft = 1 mile; 12 inches = 1 ft
1. What is the goal and what units are needed?
Goal = X inches
2. What is given and its units?
10 miles
This is a sample problem for general problem solving. The problem reads: Sam has entered into a 10 mile marathon. Use ALL of the following conversions (ratios) to determine how many inches there are in the race. Step 1. What is the goal and what units are needed? Goal = x inches. Step 2. What is given and its units? 10 miles. Step 3. Convert using factors (ratios). We set the mole ratios up so that the units cancel from top to bottom and left to right. Once all of the ratios are set up and the units cancel then we multiply across the top and bottom. Then we divide the top number by the bottom number.
3. Convert using factors (mole ratios).
10 miles = inches
633600
Given
Goal

8. Mole – Mole Conversions
When N2O5 is heated, it decomposes:
2N2O5(g)  4NO2(g) + O2(g)
a. How many moles of NO2 can be produced from 4.3 moles of N2O5?
2N2O5(g)  4NO2(g) + O2(g)
4.3 mol
? mol
4.3 mol N2O5
4 mol NO2
= moles NO2
8.6
4 mol N2O5
b. How many moles of O2 can be produced from 4.3 moles of N2O5?
Here are two examples of mole to mole calculations. Notice how to place the given amount under the formula in the equation and the unknown under the formula we are solving for. Always start with the given and make the correct mole ratio from the equation so that the units cancel left to right and top to bottom. Work through these calculations and compare your work.
2N2O5(g)  4NO2(g) + O2(g)
4.3 mol
? mol
4.3 mol N2O5
= mole O2
2.2

9. Mole – Mass Conversions
When H2O is heated, it decomposes:
2H2O(g)  2H2(g) + O2(g)
a. How many grams of O2 can be produced from 6 moles of H2O?
2H2O(g)  2H2(g) + O2(g)
6 mol
? g
6 mol H2O
32 g O 2
= g O2 32
1 mol O 2
b. What mass of water O2 can produced from 2 moles of O2?
Here are two mole to mass calculations. Remember to place the given amount under the formula in the equation and the unknown under the formula you are solving for. Always start with the given and make the correct mole ratio from the equation so that the units cancel left to right and top to bottom. Work through these calculations and compare your work.
2H2O(g)  2H2(g) + O2(g)
? g
2 mol
2 mol O2
2 mol H2O
18 g H2O
= g O2 72
1 mol O2
1 mol H2O

10. Mass – Mole Conversions
When H2O is heated, it decomposes:
2H2O(g)  2H2(g) + O2(g)
a. How many moles of O2 can be produced from 25g of H2O?
2H2O(g)  2H2(g) + O2(g)m
25 g
? mol
25 g H2O
1 mol H2O
1 mol O 2
= O2
0.78 mol
18 g H2O
2 mole H2O
b. How many moles of water O2 can produced from 150 g O2?
Here are two mass to mole calculations. Remember to place the given amount under the formula in the equation and the unknown under the formula you are solving for. Always start with the given and make the correct mole ratio from the equation so that the units cancel left to right and top to bottom. Work through these calculations and compare your work.
2H2O(g)  2H2(g) + O2(g)
? mol
150 g
150 g O2
1 mol O2
2 mol H2O
= 9.3 moles H2O
32 g O2
1 mol O2

11. Mass to Mass Conversions
Aluminum is an active metal that when placed in hydrochloric acid produces hydrogen gas and aluminum chloride. How many grams of aluminum chloride can be produced when 3.45 grams of aluminum are reacted with an excess of hydrochloric acid?
Al(s) HCl(aq)  AlCl3(aq) H2(g)
3.45 g
? grams
3.45 g Al
= g AlCl3
17.0
Here is a mass to mass calculation. Remember to place the given amount under the formula in the equation and the unknown under the formula you are solving for. Always start with the given and make the correct mole ratio from the equation so that the units cancel left to right and top to bottom. Work through these calculations and compare your work.
We must always convert to moles.
Now use the molar mass to convert to grams.

12. Mass to Volume
Ethylene burns in oxygen to form carbon dioxide and water vapor. How many liters of water can be formed if 75 g of ethylene are consumed in this reaction?
1 mole of any gas occupies a volume of 22.4 L at STP
C2H4(g) + 3 O2(g)  2 CO2(g) + 2 H2O(g)
75 g
? L
75g C2H4
1mol C2O4
3 mol O2
22.4 L O2
57.3 L O 2 =
For mass to volume calculations start with the given and make the correct mole ratios. The last mole ratio will be the molar volume ratio. Remember 1 mole of any gas occupies a volume of 22.4 L at STP (Standard temperature and pressure). Always start with the given and make the correct mole ratio from the equation so that the units cancel left to right and top to bottom. Work through this example and compare your work.
88 g C2O4
1 mol C2O4
1mol O2
Mole to mole ratio
Mole to volume ratio

13. 1 mole of any gas occupies a volume of 22.4 L at STP
Another Mass to Volume
Calcium carbonate decomposes at high temperatures to form carbon dioxide and calcium oxide. If 50 g of CaCO2 decomposes. What volume of Carbon dioxide will be formed?
1 mole of any gas occupies a volume of 22.4 L at STP
CaCO3(s)  CO2(g) + CaO(s)
50 g
? L
50 g CaCO3
100 g CaCO3
1mol CaCO3
1mol CO2
22.4 L CO2
11.2 L CO 2 =
Here is another mass to volume calculation. Work through this calculation and compare your work.
Mole to mole ratio
Mole to volume ratio

14. 1 mole of any substance contains 6.02 x 1023 particles
Mole to Particle
Hydrogen gas reacts with oxygen gas to produce water. If 10 moles of H2 are given how many particles of O2 will react with the H2 gas?
2 H2(g) O2(g)  H2O(g)
1 mole of any substance contains 6.02 x 1023 particles
10 moles
? particles
10 mol H2
2 mol H2
1mol O2
6.02 x 1023 particles of O2
1 mol O2 =
3.0 x 1024particles of O2
For mole to particle calculations. Always start with the given and make the correct mole ratios. The last mole ratio will be Avogadro's number divided by 1mole. Remember 1 mole of any substance contains 6.02 x 1023 particles. Work through this calculation and compare your work.
Mole to mole ratio
Mole to particle ratio

15. Another Mole to Particle
Hydrogen gas reacts with oxygen gas to produce water. If 5 moles of O2 are given how many particles of H2O will be produced ?
2 H2(g) O2(g)  H2O(g)
1 mole of any substance contains 6.02 x 1023 particles
5moles
? particles
5 mol O2
1 mol O2
2mol H2O
6.02 x 1023 particles of H2O
1 mol H2O
6 x 1024particles of H2O =
Here is another mole to particle calculation. Always start with the given and make the correct mole ratios. The last mole ratio will be Avogadro's number divided by 1mole. Remember 1 mole of any substance contains 6.02 x 1023 particles. Work through this calculation and compare your work.
Mole to mole ratio
Mole to particle ratio