1
CHEM 103 General Chemistry I Module 3
Exam Portage Learning Actual Exam
2026/2027 with Detailed Rationales |
Complete Exam-Style Questions | Pass
Guaranteed – A+ Graded
TABLE OF CONTENTS
Section 1 | Stoichiometry & The Mole Concept | Q1 – Q13
Section 2 | Chemical Reactions & Balancing Equations | Q14 – Q25
Section 3 | Aqueous Solutions, Molarity & Solution Stoichiometry | Q26
– Q35
Section 4 | Thermochemistry | Q36 – Q43
Section 5 | NGN-Style Integrated Case Analysis | Q44 – Q50
Instructions: Choose the single best answer. Pass: 40 in 90 minutes.
══════════════════════════════════════
SECTION 1: STOICHIOMETRY & THE MOLE CONCEPT Q1 – Q13
══════════════════════════════════════
Question 1 of 50
A pharmaceutical researcher needs to convert a measured mass of
acetylsalicylic acid (aspirin), C9H8O4, into moles to determine the
,2
dosage for a new tablet formulation. If a single tablet contains 325 mg of
aspirin, how many moles of aspirin are present in the tablet?
A. 1.80 × 10⁻³ mol ✓ CORRECT
B. 3.25 × 10⁻¹ mol
C. 5.41 × 10⁻⁴ mol
D. 1.80 × 10⁻⁶ mol
Correct Answer: A
Rationale: Molar mass serves as the conversion factor between grams
and moles, and the molar mass of C9H8O4 is 180.16 g/mol. Dividing
0.325 g by 180.16 g/mol yields 1.80 × 10⁻³ mol. The most common error
is failing to convert milligrams to grams first, which would result in a
value that is off by a factor of 1000.
Question 2 of 50
An environmental scientist analyzes a newly discovered organic
compound to determine its elemental makeup by mass. The compound is
found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen.
What is the empirical formula for this compound?
A. C2H4O
B. CH2O ✓ CORRECT
C. CHO2
,3
D. C2H2O2
Correct Answer: B
Rationale: Assuming a 100 g sample converts the percentages directly to
grams, yielding 3.33 mol of C, 6.65 mol of H, and 3.33 mol of O.
Dividing by the smallest number of moles (3.33) gives a 1:2:1 ratio,
corresponding to CH2O. Choosing CHO2 occurs if a student mistakenly
divides the oxygen mass by the molar mass of carbon instead of oxygen
during the calculation.
Question 3 of 50
In a metallurgy lab, an unknown metal oxide is reduced to its pure metal
form. Analysis shows the compound is 72.4% iron and 27.6% oxygen by
mass. Knowing the empirical formula is Fe2O3, a student attempts to
find the molecular formula. If the molar mass of the compound is
approximately 160 g/mol, what is the molecular formula?
A. Fe2O3 ✓ CORRECT
B. FeO
C. Fe3O4
D. Fe4O6
Correct Answer: A
Rationale: The empirical formula mass of Fe2O3 is calculated as (2 ×
55.85) + (3 × 16.00) = 159.7 g/mol. Since the empirical mass is
, 4
essentially identical to the given molar mass, the multiplier is 1, meaning
the empirical and molecular formulas are the same. Selecting Fe4O6
indicates a failure to reduce the ratio to the smallest whole numbers after
dividing the molar mass by the empirical mass.
Question 4 of 50
A chemical supply company produces ammonia gas for industrial
refrigeration systems. Using the balanced equation N2 + 3 H2 → 2 NH3,
a technician calculates the number of moles of hydrogen gas required to
completely react with 4.5 moles of nitrogen gas.
A. 4.5 moles
B. 6.0 moles
C. 9.0 moles
D. 13.5 moles ✓ CORRECT
Correct Answer: D
Rationale: Stoichiometry uses the mole ratio from the balanced chemical
equation to relate reactants, and the ratio of H2 to N2 is 3:1. Multiplying
4.5 moles of N2 by 3 yields 13.5 moles of H2. Selecting 9.0 moles
results from incorrectly using a 2:1 ratio, likely confusing the coefficient
of ammonia with that of hydrogen.
Question 5 of 50
CHEM 103 General Chemistry I Module 3
Exam Portage Learning Actual Exam
2026/2027 with Detailed Rationales |
Complete Exam-Style Questions | Pass
Guaranteed – A+ Graded
TABLE OF CONTENTS
Section 1 | Stoichiometry & The Mole Concept | Q1 – Q13
Section 2 | Chemical Reactions & Balancing Equations | Q14 – Q25
Section 3 | Aqueous Solutions, Molarity & Solution Stoichiometry | Q26
– Q35
Section 4 | Thermochemistry | Q36 – Q43
Section 5 | NGN-Style Integrated Case Analysis | Q44 – Q50
Instructions: Choose the single best answer. Pass: 40 in 90 minutes.
══════════════════════════════════════
SECTION 1: STOICHIOMETRY & THE MOLE CONCEPT Q1 – Q13
══════════════════════════════════════
Question 1 of 50
A pharmaceutical researcher needs to convert a measured mass of
acetylsalicylic acid (aspirin), C9H8O4, into moles to determine the
,2
dosage for a new tablet formulation. If a single tablet contains 325 mg of
aspirin, how many moles of aspirin are present in the tablet?
A. 1.80 × 10⁻³ mol ✓ CORRECT
B. 3.25 × 10⁻¹ mol
C. 5.41 × 10⁻⁴ mol
D. 1.80 × 10⁻⁶ mol
Correct Answer: A
Rationale: Molar mass serves as the conversion factor between grams
and moles, and the molar mass of C9H8O4 is 180.16 g/mol. Dividing
0.325 g by 180.16 g/mol yields 1.80 × 10⁻³ mol. The most common error
is failing to convert milligrams to grams first, which would result in a
value that is off by a factor of 1000.
Question 2 of 50
An environmental scientist analyzes a newly discovered organic
compound to determine its elemental makeup by mass. The compound is
found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen.
What is the empirical formula for this compound?
A. C2H4O
B. CH2O ✓ CORRECT
C. CHO2
,3
D. C2H2O2
Correct Answer: B
Rationale: Assuming a 100 g sample converts the percentages directly to
grams, yielding 3.33 mol of C, 6.65 mol of H, and 3.33 mol of O.
Dividing by the smallest number of moles (3.33) gives a 1:2:1 ratio,
corresponding to CH2O. Choosing CHO2 occurs if a student mistakenly
divides the oxygen mass by the molar mass of carbon instead of oxygen
during the calculation.
Question 3 of 50
In a metallurgy lab, an unknown metal oxide is reduced to its pure metal
form. Analysis shows the compound is 72.4% iron and 27.6% oxygen by
mass. Knowing the empirical formula is Fe2O3, a student attempts to
find the molecular formula. If the molar mass of the compound is
approximately 160 g/mol, what is the molecular formula?
A. Fe2O3 ✓ CORRECT
B. FeO
C. Fe3O4
D. Fe4O6
Correct Answer: A
Rationale: The empirical formula mass of Fe2O3 is calculated as (2 ×
55.85) + (3 × 16.00) = 159.7 g/mol. Since the empirical mass is
, 4
essentially identical to the given molar mass, the multiplier is 1, meaning
the empirical and molecular formulas are the same. Selecting Fe4O6
indicates a failure to reduce the ratio to the smallest whole numbers after
dividing the molar mass by the empirical mass.
Question 4 of 50
A chemical supply company produces ammonia gas for industrial
refrigeration systems. Using the balanced equation N2 + 3 H2 → 2 NH3,
a technician calculates the number of moles of hydrogen gas required to
completely react with 4.5 moles of nitrogen gas.
A. 4.5 moles
B. 6.0 moles
C. 9.0 moles
D. 13.5 moles ✓ CORRECT
Correct Answer: D
Rationale: Stoichiometry uses the mole ratio from the balanced chemical
equation to relate reactants, and the ratio of H2 to N2 is 3:1. Multiplying
4.5 moles of N2 by 3 yields 13.5 moles of H2. Selecting 9.0 moles
results from incorrectly using a 2:1 ratio, likely confusing the coefficient
of ammonia with that of hydrogen.
Question 5 of 50
