Portage Learning CHEM 121 Module 3 Exam | Foundations of General Chemistry w/ Lab (2026) Actual Q&A PDF

CHEM 121 Module 3 | Foundations of General Chemistry
w/Lab Exam Q&A | Portage Learning
These are original practice questions written for study. They cover common CHEM 121
Module 3 | Chemical Reactions and Stoichiometry topics: chemical equations,
balancing equations, types of reactions, the mole, molar mass, Avogadro's number,
stoichiometric calculations, limiting reactants, percent yield, solution stoichiometry,
molarity, and clinical applications, with NCLEX-style framing.



Question 1:
Which of the following is the correct definition of a chemical equation?
A. A symbolic representation of a chemical reaction
B. A list of elements in a compound
C. A diagram of an atom
D. A measurement of reaction rate

Correct answer: A
Rationale: A chemical equation uses symbols and formulas to represent a chemical
reaction.



Question 2:
In a chemical equation, the substances on the left side of the arrow are called:
A. Products
B. Reactants
C. Catalysts
D. Intermediates

Correct answer: B
Rationale: Reactants are the starting substances written on the left side of the arrow.



Question 3:
In a chemical equation, the substances on the right side of the arrow are called:
A. Reactants
B. Products
C. Catalysts
D. Intermediates

,Correct answer: B
Rationale: Products are the substances formed and written on the right side of the
arrow.



Question 4:
What does the arrow (→) in a chemical equation represent?
A. Equality
B. Yields or produces
C. Reversibility
D. Equilibrium

Correct answer: B
Rationale: The arrow means "yields" or "produces," indicating the direction of the
reaction.



Question 5:
Which of the following is a balanced chemical equation?
A. H₂ + O₂ → H₂O
B. 2H₂ + O₂ → 2H₂O
C. H₂ + O₂ → 2H₂O
D. 2H₂ + 2O₂ → 2H₂O

Correct answer: B
Rationale: 2H₂ + O₂ → 2H₂O has equal numbers of each atom on both sides.



Question 6:
When balancing a chemical equation, you may change:
A. Subscripts
B. Coefficients
C. Formulas
D. Elements

Correct answer: B
Rationale: Only coefficients may be changed when balancing; subscripts define the
compound.



Question 7:
Balance the equation: __Fe + __O₂ → __Fe₂O₃
A. 2, 3, 1

, B. 4, 3, 2
C. 3, 2, 1
D. 1, 1, 1

Correct answer: B
Rationale: 4Fe + 3O₂ → 2Fe₂O₃ balances iron and oxygen.



Question 8:
Balance the equation: __CH₄ + __O₂ → __CO₂ + __H₂O
A. 1, 1, 1, 1
B. 1, 2, 1, 2
C. 2, 2, 2, 2
D. 1, 3, 1, 2

Correct answer: B
Rationale: CH₄ + 2O₂ → CO₂ + 2H₂O balances carbon, hydrogen, and oxygen.



Question 9:
Balance the equation: __Na + __Cl₂ → __NaCl
A. 1, 1, 1
B. 2, 1, 2
C. 1, 2, 2
D. 2, 2, 2

Correct answer: B
Rationale: 2Na + Cl₂ → 2NaCl balances sodium and chlorine.



Question 10:
Balance the equation: __KClO₃ → __KCl + __O₂
A. 1, 1, 1
B. 2, 2, 3
C. 2, 1, 3
D. 1, 2, 3

Correct answer: B
Rationale: 2KClO₃ → 2KCl + 3O₂ balances potassium, chlorine, and oxygen.



Question 11:
Balance the equation: __Al + __HCl → __AlCl₃ + __H₂