,CHEM 103 Module 3 | Practice Q&A | 2026/2027 | Chemistry |
Portage Learning | 100% PASS
1. Balance the following chemical equation: ___ Fe + ___ O₂ → ___ Fe₂O₃
A) 2, 1, 1
B) 3, 2, 1
C) 4, 3, 2
D) 1, 1, 1
Correct Answer: 4, 3, 2
Rationale: The balanced equation is 4Fe + 3O₂ → 2Fe₂O₃. There are 4 Fe
atoms and 6 O atoms on both sides. Coefficients must be whole numbers in
the smallest ratio.
2. Balance the following chemical equation: ___ CH₄ + ___ O₂ → ___ CO₂ + ___
H₂O
A) 1, 2, 1, 2
B) 1, 1, 1, 2
C) 1, 2, 2, 1
D) 2, 3, 2, 3
Correct Answer: 1, 2, 1, 2
Rationale: The balanced equation is CH₄ + 2O₂ → CO₂ + 2H₂O. Carbon and
hydrogen are balanced first, then oxygen. There are 4 H on each side (CH₄
and 2H₂O) and 4 O (2O₂ and CO₂ + 2H₂O).
3. Balance the following chemical equation: ___ Al + ___ HCl → ___ AlCl₃ + ___
H₂
,A) 1, 3, 1, 3
B) 2, 6, 2, 3
C) 2, 3, 2, 3
D) 1, 6, 2, 3
Correct Answer: 2, 6, 2, 3
Rationale: The balanced equation is 2Al + 6HCl → 2AlCl₃ + 3H₂. There are 2
Al, 6 H, and 6 Cl on each side. This is a single replacement reaction.
4. Balance the following chemical equation: ___ C₃H₈ + ___ O₂ → ___ CO₂ + ___
H₂O
A) 1, 5, 3, 4
B) 1, 3, 3, 4
C) 2, 10, 6, 8
D) 1, 4, 3, 4
Correct Answer: 1, 5, 3, 4
Rationale: The balanced equation is C₃H₈ + 5O₂ → 3CO₂ + 4H₂O. Carbon (3)
and hydrogen (8) are balanced first, then oxygen: 5O₂ provides 10 O atoms,
and 3CO₂ + 4H₂O provides 6 + 4 = 10 O atoms.
5. What type of reaction is represented by the equation: 2H₂ + O₂ → 2H₂O?
A) Synthesis
B) Decomposition
C) Single replacement
D) Double replacement
, Correct Answer: Synthesis
Rationale: In a synthesis reaction, two or more reactants combine to form a
single product. Here, hydrogen and oxygen combine to form water. This is
also a combustion reaction.
6. What type of reaction is represented by the equation: 2KClO₃ → 2KCl +
3O₂?
A) Synthesis
B) Decomposition
C) Single replacement
D) Double replacement
Correct Answer: Decomposition
Rationale: In a decomposition reaction, a single compound breaks down into
two or more simpler substances. Potassium chlorate decomposes into
potassium chloride and oxygen gas.
7. What type of reaction is represented by the equation: Zn + CuSO₄ →
ZnSO₄ + Cu?
A) Synthesis
B) Decomposition
C) Single replacement
D) Double replacement
Correct Answer: Single replacement
Portage Learning | 100% PASS
1. Balance the following chemical equation: ___ Fe + ___ O₂ → ___ Fe₂O₃
A) 2, 1, 1
B) 3, 2, 1
C) 4, 3, 2
D) 1, 1, 1
Correct Answer: 4, 3, 2
Rationale: The balanced equation is 4Fe + 3O₂ → 2Fe₂O₃. There are 4 Fe
atoms and 6 O atoms on both sides. Coefficients must be whole numbers in
the smallest ratio.
2. Balance the following chemical equation: ___ CH₄ + ___ O₂ → ___ CO₂ + ___
H₂O
A) 1, 2, 1, 2
B) 1, 1, 1, 2
C) 1, 2, 2, 1
D) 2, 3, 2, 3
Correct Answer: 1, 2, 1, 2
Rationale: The balanced equation is CH₄ + 2O₂ → CO₂ + 2H₂O. Carbon and
hydrogen are balanced first, then oxygen. There are 4 H on each side (CH₄
and 2H₂O) and 4 O (2O₂ and CO₂ + 2H₂O).
3. Balance the following chemical equation: ___ Al + ___ HCl → ___ AlCl₃ + ___
H₂
,A) 1, 3, 1, 3
B) 2, 6, 2, 3
C) 2, 3, 2, 3
D) 1, 6, 2, 3
Correct Answer: 2, 6, 2, 3
Rationale: The balanced equation is 2Al + 6HCl → 2AlCl₃ + 3H₂. There are 2
Al, 6 H, and 6 Cl on each side. This is a single replacement reaction.
4. Balance the following chemical equation: ___ C₃H₈ + ___ O₂ → ___ CO₂ + ___
H₂O
A) 1, 5, 3, 4
B) 1, 3, 3, 4
C) 2, 10, 6, 8
D) 1, 4, 3, 4
Correct Answer: 1, 5, 3, 4
Rationale: The balanced equation is C₃H₈ + 5O₂ → 3CO₂ + 4H₂O. Carbon (3)
and hydrogen (8) are balanced first, then oxygen: 5O₂ provides 10 O atoms,
and 3CO₂ + 4H₂O provides 6 + 4 = 10 O atoms.
5. What type of reaction is represented by the equation: 2H₂ + O₂ → 2H₂O?
A) Synthesis
B) Decomposition
C) Single replacement
D) Double replacement
, Correct Answer: Synthesis
Rationale: In a synthesis reaction, two or more reactants combine to form a
single product. Here, hydrogen and oxygen combine to form water. This is
also a combustion reaction.
6. What type of reaction is represented by the equation: 2KClO₃ → 2KCl +
3O₂?
A) Synthesis
B) Decomposition
C) Single replacement
D) Double replacement
Correct Answer: Decomposition
Rationale: In a decomposition reaction, a single compound breaks down into
two or more simpler substances. Potassium chlorate decomposes into
potassium chloride and oxygen gas.
7. What type of reaction is represented by the equation: Zn + CuSO₄ →
ZnSO₄ + Cu?
A) Synthesis
B) Decomposition
C) Single replacement
D) Double replacement
Correct Answer: Single replacement
