1. Basic
Concepts on
Stoichiometry
Mr. Ronnie Z. Valenciano Jr.
Bachelor of Secondary Education
Major in Biological Science

3. What is a MOLE?
• It is the SI unit of the quantity of matter.
• It represents a specific quantity of atoms, ions
or molecules.
23
1 mole = 6.02 x 10 Avogadro’s number

4. Mole – Mass Relationship
Steps:
1. Get the molecular mass of the given
substance.
2. Then use the conversion factor remembering
that one mole of any substance has a mass,
in grams, equal to its molecular (atomic)
mass.
3. Accomplish the mathematical equation.

5. Exercises on mole – mass relationship.
• What is the mass of 2 mol of NH3?
• A container holds 45 g of sugar (C6H12O6).
How many moles of sugar are present?
• How many moles are present in 27.0 g of
water?

6. Balancing Equations
Steps:
1. Determine the reactants and
products.
2. Assemble the parts of the
chemical reaction.
3. Balance the equation

7. Balance the following equation:
1. N2 + H2 NH3
2. NH3 + O2 N2 + H20
3. Al + S Al2S3
4. C6H12O6 CO2 + H2O

8. Mass – Mass Relationship
Steps:
1. Write the balanced equations.
2. Find the number of moles of the given
substance.
3. Inspect the balance equation to determine
the ratio moles of required substance to
moles of given substance.
4. Express the moles of required substance in
terms of gram, then convert moles to grams.

9. Stoichiometry overview
•Recall that in stoichiometry the mole ratio
provides a necessary conversion factor:
molar mass of x molar mass of y
grams (x) moles (x) moles (y) grams (y)
mole ratio from balanced equation
• We can do something similar with solutions:
mol/L of x mol/L of y
volume (x) moles (x) moles (y) volume (y)
mole ratio from balanced equation

10. Problem Solving
Consider the reaction of ammonia with oxygen
to produced nitrogen monoxide and water.
4NH3 + 5O2 4NO + 6H2O
If 2.85 g of ammonia reacts completely with
excess oxygen what mass of water can be
obtained?

11. • The principal constituent of natural gas is
methane, which burns in air according to the
reaction.
CH4 + 2O2 CO2 + 2H2O
How many grams of oxygen gas are needed to
produce 3.50 g of carbon dioxide?

12. • Tungsten (W) metal, which is used to make
incandescent bulb filaments is produced by
the reaction,
WO3 + 3H2 3H2O + W
How many grams of hydrogen gas are needed
to produced 1.00g of tungsten?

13. Calcium hydroxide is sometimes used in water
treatment plants to clarify water for residential
use. Calculate the volume of 0.0250 mol/L
calcium hydroxide solution that can be
completely reacted with 25.0 mL of 0.125 mol/L
aluminum sulfate solution.
Al2(SO4)3(aq) + 3Ca(OH)2(aq) 2Al(OH)3(s) + 3CaSO4(s)
# L Ca(OH)2=
0.0250 0.125 mol Al2(SO4)3 3 mol Ca(OH)2 L Ca(OH)2
x x x
L Al2(SO4)3 L Al2(SO4)3 1 mol Al2(SO4)3 0.0250 mol
Ca(OH)2
= 0.375 L Ca(OH)2

14. • H2SO4 reacts with NaOH, producing water and
sodium sulfate. What volume of 2.0 M H2SO4
will be required to react completely with 75 mL
of 0.50 mol/L NaOH?
H2SO4(aq) + 2NaOH(aq) 2H2O + Na2SO4(aq)
# L H2SO4=
0.50 mol NaOH 1 mol H2SO4
0.075 L NaOH x x
L NaOH 2 mol NaOH
L H2SO4
x = 0.009375 L = 9.4 mL
2.0 mol H2SO4

15. How many moles of Fe(OH)3 are produced
when 85.0 L of iron(III) sulfate at a
concentration of 0.600 mol/L reacts with
excess NaOH?
Fe2(SO4)3(aq) + 6NaOH(aq) 2Fe(OH)3(s) +
3Na2SO4(aq)
# mol Fe(OH)3=
85 L Fe2(SO4)3 x 0.600 mol Fe2(SO4)3 x 2 mol Fe(OH)3
L Fe2(SO4)3 1 mol Fe2(SO4)3
= 102 mol