CHEMISTRY OBJECTIVE ASSESSMENT
WGU D425 Intro to Chemistry
Objective Assessment A+
Actual Exam 2025/2026 — 2026/2027
Official-Style Practice Exam • Foundational University Level • Application & Analysis
A+ QUESTIONS 5 SECTIONS 100% RATIONALES
VERIFIED COMPLETE INCLUDED
CATEGORIES
Matter, Measurement & Significant Figures
Atomic Structure & Periodic Trends
Chemical Bonding & Molecular Geometry
Chemical Reactions, Stoichiometry & Moles
Gases, Solutions, Acids/Bases & Organic Basics
STUVIAACTUALEXAM
Passing Score: 75% • 1 Mark per Question • Application/Analysis Level
, Matter, Measurement & Significant Figures
Q1. A laboratory technician measures the mass of a solid sample three times and obtains 12.48 g, 12.51 g, and 12.49
g. The accepted true value is 12.50 g. The technician needs to evaluate both the precision and accuracy of these
measurements before reporting results to the quality-control team.
A. The measurements are both precise and accurate.
B. The measurements are accurate but not precise.
C. The measurements are precise but not accurate.
D. The measurements lack both precision and accuracy.
Correct Answer: A
Rationale: Precision refers to the closeness of repeated measurements to one another; the three values differ by only 0.03 g.
Accuracy refers to closeness to the true value; the average is essentially 12.50 g. Therefore both criteria are satisfied.
Q2. A student records the volume of a liquid as 25.60 mL using a graduated cylinder that is calibrated to the nearest
0.01 mL. When this volume is later converted to liters for a stoichiometric calculation, the student must retain the
correct number of significant figures.
A. 0.0256 L
B. 2.56 × 10■² L
C. 0.02560 L
D. 0.026 L
Correct Answer: C
Rationale: The measured value 25.60 mL already contains four significant figures, including the trailing zero after the decimal.
Dividing by 1000 moves the decimal but does not change the number of significant figures, so 0.02560 L is required.
Q3. During a density determination, a metal cylinder is found to have a mass of 48.72 g and a volume of 5.60 cm³. The
student must calculate density and then compare it with known metal densities to identify the sample.
A. 8.7 g/cm³
B. 8.70 g/cm³
C. 0.115 g/cm³
D. 8.700 g/cm³
Correct Answer: B
Rationale: Density = mass/volume = 48.72 g / 5.60 cm³. The volume measurement limits the result to three significant figures, giving
8.70 g/cm³ after proper rounding.
Q4. A pharmaceutical formulation requires 2.50 × 10■³ kg of an active ingredient. The laboratory balance reads only in
grams. The technician must convert the required mass correctly before weighing.
A. 0.250 g
B. 250 g
C. 25.0 g
D. 2.50 g
Correct Answer: D
Rationale: 1 kg = 1000 g, so 2.50 × 10■³ kg × 1000 g/kg = 2.50 g. The scientific-notation conversion preserves the three significant
figures of the original quantity.
, Matter, Measurement & Significant Figures
Q5. A mixture contains sand, salt, and iron filings. A student is asked to separate the components using only physical
methods available in a general-chemistry laboratory. The first step chosen will determine the efficiency of the
entire separation sequence.
A. Use a magnet to remove the iron filings.
B. Dissolve the mixture in water and filter.
C. Heat the mixture to sublime the salt.
D. Centrifuge the dry mixture to isolate sand.
Correct Answer: A
Rationale: Iron filings are ferromagnetic and can be removed cleanly with a magnet without affecting the other two components.
Subsequent dissolution of salt and filtration of sand complete the separation efficiently.
Q6. An unknown pure substance melts sharply at 114 °C and does not conduct electricity in the solid state or when
molten. The laboratory supervisor asks the student to classify the substance on the basis of these observations.
A. Metallic solid
B. Ionic compound
C. Covalent molecular solid
D. Network covalent solid
Correct Answer: C
Rationale: A sharp melting point indicates a pure substance. Lack of electrical conductivity in both solid and liquid states rules out
metallic and ionic solids. Network covalent solids typically have extremely high melting points, leaving a molecular covalent
solid as the consistent classification.
Q7. A student performs the calculation (12.6 × 3.42) + 0.58 and must report the final answer with the correct number of
significant figures according to addition and multiplication rules.
A. 44
B. 43.7
C. 43.67
D. 43.672
Correct Answer: B
Rationale: First multiply: 12.6 × 3.42 = 43.092 (three significant figures). Adding 0.58 gives 43.672, but the addition rule limits the
result to the tenths place because 0.58 is known only to the hundredths; the properly rounded value is therefore 43.7.
Q8. A sample of pure copper is heated from 22.0 °C to 85.0 °C. The laboratory notebook records both the initial and
final temperatures to the nearest 0.1 °C. When calculating the temperature change for a subsequent heat-capacity
computation, the student must determine the correct significant figures for ∆T.
A. 60 °C
B. 63.00 °C
C. 63 °C
D. 63.0 °C
Correct Answer: D
Rationale: Subtraction of measured values retains the least precise decimal place. Both temperatures are recorded to the tenths
place, so ∆T = 85.0 − 22.0 = 63.0 °C retains one digit after the decimal.
WGU D425 Intro to Chemistry
Objective Assessment A+
Actual Exam 2025/2026 — 2026/2027
Official-Style Practice Exam • Foundational University Level • Application & Analysis
A+ QUESTIONS 5 SECTIONS 100% RATIONALES
VERIFIED COMPLETE INCLUDED
CATEGORIES
Matter, Measurement & Significant Figures
Atomic Structure & Periodic Trends
Chemical Bonding & Molecular Geometry
Chemical Reactions, Stoichiometry & Moles
Gases, Solutions, Acids/Bases & Organic Basics
STUVIAACTUALEXAM
Passing Score: 75% • 1 Mark per Question • Application/Analysis Level
, Matter, Measurement & Significant Figures
Q1. A laboratory technician measures the mass of a solid sample three times and obtains 12.48 g, 12.51 g, and 12.49
g. The accepted true value is 12.50 g. The technician needs to evaluate both the precision and accuracy of these
measurements before reporting results to the quality-control team.
A. The measurements are both precise and accurate.
B. The measurements are accurate but not precise.
C. The measurements are precise but not accurate.
D. The measurements lack both precision and accuracy.
Correct Answer: A
Rationale: Precision refers to the closeness of repeated measurements to one another; the three values differ by only 0.03 g.
Accuracy refers to closeness to the true value; the average is essentially 12.50 g. Therefore both criteria are satisfied.
Q2. A student records the volume of a liquid as 25.60 mL using a graduated cylinder that is calibrated to the nearest
0.01 mL. When this volume is later converted to liters for a stoichiometric calculation, the student must retain the
correct number of significant figures.
A. 0.0256 L
B. 2.56 × 10■² L
C. 0.02560 L
D. 0.026 L
Correct Answer: C
Rationale: The measured value 25.60 mL already contains four significant figures, including the trailing zero after the decimal.
Dividing by 1000 moves the decimal but does not change the number of significant figures, so 0.02560 L is required.
Q3. During a density determination, a metal cylinder is found to have a mass of 48.72 g and a volume of 5.60 cm³. The
student must calculate density and then compare it with known metal densities to identify the sample.
A. 8.7 g/cm³
B. 8.70 g/cm³
C. 0.115 g/cm³
D. 8.700 g/cm³
Correct Answer: B
Rationale: Density = mass/volume = 48.72 g / 5.60 cm³. The volume measurement limits the result to three significant figures, giving
8.70 g/cm³ after proper rounding.
Q4. A pharmaceutical formulation requires 2.50 × 10■³ kg of an active ingredient. The laboratory balance reads only in
grams. The technician must convert the required mass correctly before weighing.
A. 0.250 g
B. 250 g
C. 25.0 g
D. 2.50 g
Correct Answer: D
Rationale: 1 kg = 1000 g, so 2.50 × 10■³ kg × 1000 g/kg = 2.50 g. The scientific-notation conversion preserves the three significant
figures of the original quantity.
, Matter, Measurement & Significant Figures
Q5. A mixture contains sand, salt, and iron filings. A student is asked to separate the components using only physical
methods available in a general-chemistry laboratory. The first step chosen will determine the efficiency of the
entire separation sequence.
A. Use a magnet to remove the iron filings.
B. Dissolve the mixture in water and filter.
C. Heat the mixture to sublime the salt.
D. Centrifuge the dry mixture to isolate sand.
Correct Answer: A
Rationale: Iron filings are ferromagnetic and can be removed cleanly with a magnet without affecting the other two components.
Subsequent dissolution of salt and filtration of sand complete the separation efficiently.
Q6. An unknown pure substance melts sharply at 114 °C and does not conduct electricity in the solid state or when
molten. The laboratory supervisor asks the student to classify the substance on the basis of these observations.
A. Metallic solid
B. Ionic compound
C. Covalent molecular solid
D. Network covalent solid
Correct Answer: C
Rationale: A sharp melting point indicates a pure substance. Lack of electrical conductivity in both solid and liquid states rules out
metallic and ionic solids. Network covalent solids typically have extremely high melting points, leaving a molecular covalent
solid as the consistent classification.
Q7. A student performs the calculation (12.6 × 3.42) + 0.58 and must report the final answer with the correct number of
significant figures according to addition and multiplication rules.
A. 44
B. 43.7
C. 43.67
D. 43.672
Correct Answer: B
Rationale: First multiply: 12.6 × 3.42 = 43.092 (three significant figures). Adding 0.58 gives 43.672, but the addition rule limits the
result to the tenths place because 0.58 is known only to the hundredths; the properly rounded value is therefore 43.7.
Q8. A sample of pure copper is heated from 22.0 °C to 85.0 °C. The laboratory notebook records both the initial and
final temperatures to the nearest 0.1 °C. When calculating the temperature change for a subsequent heat-capacity
computation, the student must determine the correct significant figures for ∆T.
A. 60 °C
B. 63.00 °C
C. 63 °C
D. 63.0 °C
Correct Answer: D
Rationale: Subtraction of measured values retains the least precise decimal place. Both temperatures are recorded to the tenths
place, so ∆T = 85.0 − 22.0 = 63.0 °C retains one digit after the decimal.
