1. Stoichiometry

2. Stoichiometry is the
study of quantitative
relationships in
chemical reactions.

3. The basic idea used in
solving stoichiometric
problems is the mole
concept.

4. A short review

5. Molecular weight is the
sum of the atomic
weights of all the atoms
in a molecule.
A molecule is the
smallest unit of a
covalent compound.

6. What is a mole?

7. A mole (mol) is a SI base
unit used to measure the
amount of material in a
chemical sample.

8. 1 mole of H2O contains
6.022 x 1023 H2O molecules
(Avogadro’s number)

9. A coefficient in a balanced
chemical equation indicates
the number of moles of a
chemical compound involved in
a chemical reaction.
2H2 + O2  2H2O

10. The coefficients give you the
mole ration of the compounds
involved in the reaction.
2H2 + O2  2H2O
The mole ratio of hydrogen to
oxygen is 2:1 (for every one
oxygen put into the reaction, 2
moles of hydrogen are also
needed to put into the reaction)

11. The unit of moles
provides a “bridge” to
mathematically convert
between several different
aspects of chemical
compounds.

13. Moles link an abstract
chemical equation to a
concrete unit of
measurement (grams,
Liters, number of
molecules)

14. For example:
1 mole = 6.02 x 1023 molecules
1 mole = molecular mass of a
substance
1 mole = 22.4 L of a substance
at STP (standard temperature
and pressure)

15. For example:
1 mol Cl = 6.02 x 1023 molecules Cl
1 mol H2O = 6.02 x 1023 molecules
H 2O
1 mol Cl = 35.45g Cl
1 mol H2O = 18.01g H2O
1 mol Cl = 22.4L Cl @ STP
1 mol H2O = 22.4L H2O @ ATP

16. There are several types of
calculations that can be
used in Stoichiometry.

17. Mole – mole
calculations

18. Involves 1
conversion
factor

19. The object of this type of
problem is to calculate the
moles of one substance
when given the number of
moles of different
substance.

20. Example: Magnesium
hydroxide reacts with carbonic
acid. How many moles of water
will be produced from
3.5 moles of magnesium
hydroxide?
You are given the moles of one
substance and asked to find the
moles of another substance.

21. Example: How many moles
of ammonia can be produced
from 8.00 moles of hydrogen
reacting with nitrogen?

22. Example:
K2Cr2O7 + 6KI + 7H2SO4  Cr2
(SO4)3 + 4K2SO4 + 3I2 + 7H2O
Calculate the number of moles of
potassium dichromate that will
react with 2.0 moles of potassium
iodide. Calculate the number of
moles of iodine that will be
produced from 2.0 moles of
potassium iodide.

23. Mole – mass calculations

24. Involves 2
conversion
factors

25. The object of this type of
problem is to calculate
the moles of one
substance when given the
mass of different
substance.
Or vise versa

26. Example:
What mass of hydrogen can be
produced by reacting
6.0 moles of aluminum with
hydrochloric acid?
You are given the moles of one
substance and asked to find the
mass of another substance.

27. Example: How much
carbon dioxide is
produced by the complete
combustion of 0.0492 mol
of propane, C3H8?

28. Example: How many
moles of water will be
produced from 14.6 g
propane in the
combustion of propane?

29. Mass – Mass calculations

30. Involves 3
conversion
factors

31. The object of this type of
problem is to calculate
the mass of one
substance when given the
mass of different
substance.

32. Example:
How much carbon dioxide is
produced by the complete
combustion of
100.0 g of propane, C3H8?
You are given the moles of one
substance and asked to find the
mass of another substance.

33. Example: Magnesium
chloride reacts with
sulfuric acid. How much
sulfuric acid is needed to
produce 26.3 g of
magnesium sulfate?

34. Calculations
involving Liters
and number of
molecules

35. Example: How many moles
of ammonia can be produced
from 1.03 Liters of hydrogen
reacting with nitrogen at
STP?

36. Example: How many carbon
dioxide molecules are
produced by the complete
combustion of 32.00 grams
of propane, C3H8?