1. 2 H2 + O2 → 2 H2O 2 mol H2 for every 1 mol O2
Mol to Mol Ratios
In chemical calculations, mol ratios convert moles of one substance to moles of another substance.
mol ratio:
coefficients of a balanced equation
2 H O2 → 2 H2O
2 mol H2 for every 1 mol O2

2. 2 H2 + O2 → 2 H2O OR 2 mol H2 for every 2 mol H2O
Mol to Mol Ratios
In chemical calculations, mol ratios convert moles of one substance to moles of another substance.
mol ratio:
coefficients of a balanced equation
2 H O2 → 2 H2O OR
2 mol H2 for every 2 mol H2O

3. 2 H2 + O2 → 2 H2O OR 1 mol O2 for every 2 mol H2O
Mol to Mol Ratios
In chemical calculations, mol ratios convert moles of one substance to moles of another substance.
mol ratio:
coefficients of a balanced equation
2 H O2 → 2 H2O OR
1 mol O2 for every 2 mol H2O

4. 2 H O2 → 2 H2O
There are 6 mol to mol ratios that can be written from this balanced equation:
2 mol H2 1 mol O2 2 mol H2O
1 mol O2 2 mol H2 2 mol H2
2 mol H2O 2 mol H2O 1 mol O2
To determine the number of moles in a sample of a compound, first measure the mass of the sample. Then use the molar mass to calculate the number of moles in that mass. 4

5. We must use MOLES to calculate, but…
We don’t measure moles in the lab, we measure mass (in grams), but…
We can’t convert
grams A to grams B, so…
We convert grams to moles
using…
Molar Mass (g/mol) from…
the Periodic Table
To determine the number of moles in a sample of a compound, first measure the mass of the sample. Then use the molar mass to calculate the number of moles in that mass.

6. In a typical stoichiometric problem:
1) Convert grams to moles (if necessary)
using the molar mass (from PT)
2) Convert moles (given) to moles (wanted)
using the mol ratio (from coefficients)
3) Convert moles to grams (if necessary)
1 mol A .
grams A
_ mol B
mol A
grams B
1 mol B
grams A x x x =
1) molar mass
2) mole ratio
3) molar mass

7. Mg + 2 HCl → MgCl2 + H2 4.0 mol Mg x Moles to Moles (Calculation #1)
Handout: 4 Types of Stoichiometric Calculations
Moles to Moles (Calculation #1)
How many moles of hydrogen gas (H2) are produced from 4.0 mol Mg?
Mg HCl → MgCl2 + H2
4.0 mol Mg x 7

8. 2) moles (given) to moles (wanted) using the mol ratio
1) grams to moles
using the molar mass
2) moles (given) to moles (wanted)
using the mol ratio
3) moles to grams
1 mol A .
grams A
_ mol B
mol A
grams B
1 mol B
grams A x x x =
1) molar mass
2) mole ratio
3) molar mass
(coefficients)

9. Mg + 2 HCl → MgCl2 + H2 1 mol H2 1 mol Mg 4.0 mol Mg x = 4.0 mol H2
Handout: 4 Types of Stoichiometric Calculations
Moles to Moles (Calculation #1)
How many moles of hydrogen gas (H2) are produced from 4.0 mol Mg?
Mg HCl → MgCl2 + H2
1 mol H2
1 mol Mg
4.0 mol Mg x =
4.0 mol H2
mol ratio 9

10. Mg + 2 HCl → MgCl2 + H2 4.0 mol HCl x Moles to Moles (Calculation #1)
How many moles of hydrogen gas (H2) are produced from 4.0 mol HCl?
Mg HCl → MgCl2 + H2
4.0 mol HCl x 10

11. 2) moles (given) to moles (wanted) using the mol ratio
1) grams to moles
using the molar mass
2) moles (given) to moles (wanted)
using the mol ratio
3) moles to grams
1 mol A .
grams A
_ mol B
mol A
grams B
1 mol B
grams A x x x =
1) molar mass
2) mole ratio
3) molar mass
(coefficients)

12. Mg + 2 HCl → MgCl2 + H2 1 mol H2 2 mol HCl 4.0 mol HCl x = 2.0 mol H2
Moles to Moles (Calculation #1)
How many moles of hydrogen gas (H2) are produced from 4.0 mol HCl?
Mg HCl → MgCl2 + H2
1 mol H2
2 mol HCl
4.0 mol HCl x =
2.0 mol H2
mol ratio 12

13. Mg + 2 HCl → MgCl2 + H2 Moles to Grams (Calculation #2)
How many grams of H2 are produced from mol HCl?
Mg HCl → MgCl2 + H2
4.00 mol HCl x 13

14. (coefficients) (from PT)
1) grams to moles
using the molar mass
2) moles (given) to moles (wanted)
using the mol ratio
3) moles to grams
1 mol A .
grams A
_ mol B
mol A
grams B
1 mol B
grams A x x x =
1) molar mass
2) mole ratio
3) molar mass
(coefficients)
(from PT)

15. Mg + 2 HCl → MgCl2 + H2 mol ratio molar mass
Moles to Grams (Calculation #2)
How many grams of H2 are produced from mol HCl?
Mg HCl → MgCl2 + H2
1 mol H2
2 mol HCl
2.02 g H2
1 mol H2
4.00 mol HCl x x =
4.04 g H2
mol ratio
molar mass 15

16. Mg + 2 HCl → MgCl2 + H2 Grams to Moles (Calculation #3)
How many mol of H2 are produced from
48 g Mg?
Mg HCl → MgCl2 + H2
48 g Mg x 16

17. (from PT) (coefficients)
1) grams to moles
using the molar mass
2) moles (given) to moles (wanted)
using the mol ratio
3) moles to grams
1 mol A .
grams A
_ mol B
mol A
grams B
1 mol B
grams A x x x =
1) molar mass
2) mole ratio
3) molar mass
(from PT)
(coefficients)

18. Mg + 2 HCl → MgCl2 + H2 molar mass mol ratio
Grams to Moles (Calculation #3)
How many mol of H2 are produced from
48 g Mg?
Mg HCl → MgCl2 + H2
1 mol Mg
24.31 g Mg
1 mol H2
1 mol Mg
48 g Mg x x =
2.0 mol H2
molar mass
mol ratio 18

19. Mg + 2 HCl → MgCl2 + H2 Grams to Grams (Calculation #4)
How many grams of H2 are produced from
18 g HCl?
Mg HCl → MgCl2 + H2
18 g HCl x 19

20. (from PT) (coefficients) (from PT)
1) grams to moles
using the molar mass
2) moles (given) to moles (wanted)
using the mol ratio
3) moles to grams
1 mol A .
grams A
_ mol B
mol A
grams B
1 mol B
grams A x x x =
1) molar mass
2) mole ratio
3) molar mass
(from PT)
(coefficients)
(from PT)

21. Mg + 2 HCl → MgCl2 + H2 mol ratio molar mass molar mass
Grams to Grams (Calculation #4)
How many grams of H2 are produced from
18 g HCl?
Mg HCl → MgCl2 + H2
1 mol HCl
36.46 g HCl
1 mol H2
2 mol HCl
2.02 g H2
1 mol H2
18 g HCl x x x =
0.50 g H2
mol ratio
molar mass
molar mass 21

22. C2H5OH(l) + 3 O2(g)  2 CO2(g) + 3 H2O(g)
Quick Quiz!
1. How many moles of water are produced from burning 4.00 mol C2H5OH (ethanol)?
C2H5OH(l) + 3 O2(g)  2 CO2(g) + 3 H2O(g)
3.00 mol H2O
4.00 mol H2O
12.0 mol H2O
1.33 mol H2O
mol ratio
3 mol H2O
1 mol C2H5OH
4.0 mol C2H5OH x =

23. C2H5OH(l) + 3 O2(g)  2 CO2(g) + 3 H2O(g)
Quick Quiz.
2. How many grams of oxygen gas (O2) are needed to react with 2.00 mol of C2H5OH ?
C2H5OH(l) + 3 O2(g)  2 CO2(g) + 3 H2O(g)
6.00 g O2
21.1 g O2
96.0 g O2
192 g O2
molar mass
mol ratio
3 mol O2 .
1 mol C2H5OH
2.0 mol C2H5OH x
32.00 g O2
1 mol O2 x =