Classroom Demonstration in Physical Science about Stoichiometry Calculating the amount of Substance used or produced in a chemical reaction by using algebraic expression

1. Lyndy C. Arong, LPT
STOICHIOMETRY

2. STOICHIOMETRY
 (in Greek) stoikhein means element and metron
means measure
 the measure of elements
 involves the use of relationships between
reactants and/or products in a chemical
reaction to determine desired quantitative data

3. STOICHIOMETRY OF HEAT
 Important Note:
 the coefficients of the chemical equation
must be balanced first
 unit: kiloJoules (kJ)

4. DOUBLE THIS, THAT
Double, double that, that
Double, double this, this
Double that
Double this
Double, double, this that

5. LAW OF CONSERVATION
OF ENERGY
Energy can neither be created nor destroyed;
rather, it can only be transformed
or transferred from one form to another.

7. At the end of the lesson,
learners will be able to:
a. Calculate the amount of
substances used or produced in
a chemical reaction by using
algebraic expression.
LESSON
OBJECTIVE

8. ALGEBRAIC TECHNIQUE
First, list the ff:
unknown quantity name (uqn),
unknown quantity symbol (uqs),
unknown unit name (uun), and
unknown unit symbol (uus).
uqn: uun:
uqs: uus:

9. ALGEBRAIC TECHNIQUE
1. Define the unknown variable.
2. Interpret the problem and
write an algebraic statement
that leads to the solution.
3. Solve the algebraic statement.
4. Write your final answer in sentence form.

10. SAMPLE PROBLEM
What mass (g) of Fe will be produced from
152.6 grams of CO and an excess of Fe2O3?
The molar mass of CO is 28.01 g/mol and the
molar mass of Fe is 55.85 g/mol.
Fe2O3 (s) + 3 CO (g) → 2 Fe (s) + 3 CO2 (g)

11. SAMPLE PROBLEM
uqn: mass uun: gram
uqs: m uus: g
m = 152.6 g CO x 1 mol CO x 2 mol Fe x 55.85 g Fe
28.01 g CO 3 mol CO 1 mol Fe
given mass MM of CO ratio of
Fe to CO
MM of Fe

12. SAMPLE PROBLEM
m = 152.6 g CO x 1 mol CO x 2 mol Fe x 55.85 g Fe
28.01 g CO 3 mol CO 1 mol Fe
given mass MM of CO ratio of
Fe to CO
MM of Fe
Important Note:
When building the algebraic statement, use the
units to guide which quantity goes where (top or
bottom). The goal is for the units to cancel out so
that you are left with your desired unit.

13. SAMPLE PROBLEM
m = 152.6 g CO x 1 mol CO x 2 mol Fe x 55.85 g Fe
28.01 g CO 3 mol CO 1 mol Fe
given mass MM of CO ratio of
Fe to CO
MM of Fe
Answer:
m = 202.8 g Fe
Therefore, 202.8 g of Fe will be produced from 152.6 g of
carbon monoxide and an excess of iron (III) oxide.

14. GROUP
ACTIVITY
GIVE THOUGHTFUL FEEDBACK
RESPECT OTHERS
ON TASK ALL THE TIME
USE SOFT VOICES
PARTICIPATE ACTIVELY
STAY WITH YOUR GROUP

15. PROBLEM 2
PROBLEM 1
What mass (g) of NaCl will be produced from
32.00 grams of Na and an excess of Cl?
The molar mass of Na is 22.99 g/mol and the
molar mass of NaCl is 58.44 g/mol.
Na(s) + Cl(s) → NaCl(s)
PROBLEM 3
What mass (g) of iron (Fe) will be produced from 232.0 grams of carbon
monoxide and an excess of iron (III) oxide? The molar mass of carbon
monoxide is 28.01 g/mol and the molar mass of iron is 55.85 g/mol.
Fe2O3(s) + 3 CO(g) → 2 Fe(s) + 3 CO2(g)
What mass (g) of AlCl3 will be produced from
95.60 grams of Al and an excess of Cl?
The molar mass of Al is 26.98 g/mol and the
molar mass of AlCl3 is 133.33 g/mol.
Al(s) + 3 Cl(s) → AlCl3(s)

16. RUBRICS
Criteria 3 2 1
Quality of
information
Informative,
accurate, and
show depth
understanding
Some
information is
not accurate
and show poor
understanding
Not informative
and not
accurate
Presentation
Skills
Group expertly
explain the
whole topic
Some topics are
not explained
well by group
Group unable
to explain the
topic
Visual Model Creative,
original, and
correlates well
Little
creativity, little
originality
Hasty done, not
creative, no
originality

17. ASSIGNMENT
 Research on the calculation of the amount of
substances used or produced in a chemical
reaction by using the step-by-step proportion
technique.

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