1
WGU D425 Introduction to Chemistry OA
Review Official Practice Exam Actual Exam
2026/2027 with Detailed Rationales | Complete
Exam-Style Questions | Pass Guaranteed – A+
Graded
TABLE OF CONTENTS
Section 1 | Matter, Measurement & The Scientific Method | Q1 – Q10
Section 2 | Atomic Structure & The Periodic Table | Q11 – Q20
Section 3 | Chemical Bonding & Molecular Geometry | Q21 – Q30
Section 4 | Chemical Reactions & Stoichiometry | Q31 – Q40
Section 5 | Solutions, Acids/Bases & NGN-Style Case Analysis | Q41 – Q50
Instructions: Choose the single best answer. Pass: 80% in 90 minutes.
══════════════════════════════════════
SECTION 1: MATTER, MEASUREMENT & THE SCIENTIFIC METHOD Q1 –
Q10
══════════════════════════════════════
Question 1 of 50
A laboratory technician is evaluating the properties of a newly synthesized liquid
to determine its potential uses. The technician notes that the liquid boils at 115°C,
has a density of 1.38 g/mL, and reacts violently with water to produce a gas.
,2
A. Boiling point and density, because they can be observed without changing the
substance's composition.
B. The reaction with water, because it produces a new substance and changes the
chemical composition. ✓ CORRECT
C. The density and the violent reaction, because both require measurement tools to
evaluate.
D. The boiling point and the reaction, because both involve energy changes in the
laboratory.
Correct Answer: B
Rationale: A chemical property describes a substance's ability to undergo a
chemical change, such as reacting violently with water to form a new gas. A
tempting wrong answer states that boiling point is a chemical property, but boiling
is only a physical change of state. On the exam, always look for whether a new
substance is formed.
Question 2 of 50
A student records the mass of a beaker as 120.45 g and adds 2.5 g of a solid
sample. The student must report the total mass to the correct number of significant
figures based on the precision of the measurements.
A. 122.95 g
B. 123.0 g
C. 123 g
D. 122.9 g ✓ CORRECT
Correct Answer: D
,3
Rationale: When adding measurements, the result must be rounded to the same
number of decimal places as the measurement with the fewest decimal places. The
trap of 122.95 g ignores the rules of addition and gives a false level of precision.
Always line up the decimal points to see which number limits the precision.
Question 3 of 50
During a field trip, a geology student collects a sample containing visible veins of
quartz embedded in solid granite. The student must correctly classify this sample
for the laboratory report.
A. Heterogeneous mixture, because the components are not uniformly distributed
and are visually distinct. ✓ CORRECT
B. Homogeneous mixture, because the minerals are mixed evenly throughout the
rock.
C. Pure compound, because the granite and quartz are chemically bonded together.
D. Pure element, because the sample consists entirely of naturally occurring earth
materials.
Correct Answer: A
Rationale: A heterogeneous mixture contains physically distinct parts that are not
uniformly distributed, such as veins of quartz in granite. A tempting wrong answer
classifies it as a homogeneous mixture, which would require the components to be
evenly distributed and indistinguishable. For the exam, if you can see distinct
pieces, it is heterogeneous.
Question 4 of 50
, 4
An environmental chemist needs to convert a water contaminant measurement
from 45 micrograms per liter to milligrams per liter for a regulatory report.
A. 0.045 mg/L
B. 4.5 mg/L
C. 0.045 mg/L
D. 0.045 mg/L ✓ CORRECT
Correct Answer: D
Rationale: Converting micrograms to milligrams requires dividing by 1,000,
moving the decimal three places to the left. The trap of 4.5 mg/L results from
incorrectly multiplying by 1,000 instead of dividing. Memorizing that milli- is
larger than micro- prevents this inversion.
Question 5 of 50
A materials scientist is tasked with identifying an unknown metal cube. The cube
has a volume of 12.5 cm³ and a mass of 52.75 g. The scientist needs to calculate
the density to compare it against known standards.
A. 0.237 g/cm³
B. 4.22 g/cm³ ✓ CORRECT
C. 65.25 g/cm³
D. 4220 g/cm³
Correct Answer: B
WGU D425 Introduction to Chemistry OA
Review Official Practice Exam Actual Exam
2026/2027 with Detailed Rationales | Complete
Exam-Style Questions | Pass Guaranteed – A+
Graded
TABLE OF CONTENTS
Section 1 | Matter, Measurement & The Scientific Method | Q1 – Q10
Section 2 | Atomic Structure & The Periodic Table | Q11 – Q20
Section 3 | Chemical Bonding & Molecular Geometry | Q21 – Q30
Section 4 | Chemical Reactions & Stoichiometry | Q31 – Q40
Section 5 | Solutions, Acids/Bases & NGN-Style Case Analysis | Q41 – Q50
Instructions: Choose the single best answer. Pass: 80% in 90 minutes.
══════════════════════════════════════
SECTION 1: MATTER, MEASUREMENT & THE SCIENTIFIC METHOD Q1 –
Q10
══════════════════════════════════════
Question 1 of 50
A laboratory technician is evaluating the properties of a newly synthesized liquid
to determine its potential uses. The technician notes that the liquid boils at 115°C,
has a density of 1.38 g/mL, and reacts violently with water to produce a gas.
,2
A. Boiling point and density, because they can be observed without changing the
substance's composition.
B. The reaction with water, because it produces a new substance and changes the
chemical composition. ✓ CORRECT
C. The density and the violent reaction, because both require measurement tools to
evaluate.
D. The boiling point and the reaction, because both involve energy changes in the
laboratory.
Correct Answer: B
Rationale: A chemical property describes a substance's ability to undergo a
chemical change, such as reacting violently with water to form a new gas. A
tempting wrong answer states that boiling point is a chemical property, but boiling
is only a physical change of state. On the exam, always look for whether a new
substance is formed.
Question 2 of 50
A student records the mass of a beaker as 120.45 g and adds 2.5 g of a solid
sample. The student must report the total mass to the correct number of significant
figures based on the precision of the measurements.
A. 122.95 g
B. 123.0 g
C. 123 g
D. 122.9 g ✓ CORRECT
Correct Answer: D
,3
Rationale: When adding measurements, the result must be rounded to the same
number of decimal places as the measurement with the fewest decimal places. The
trap of 122.95 g ignores the rules of addition and gives a false level of precision.
Always line up the decimal points to see which number limits the precision.
Question 3 of 50
During a field trip, a geology student collects a sample containing visible veins of
quartz embedded in solid granite. The student must correctly classify this sample
for the laboratory report.
A. Heterogeneous mixture, because the components are not uniformly distributed
and are visually distinct. ✓ CORRECT
B. Homogeneous mixture, because the minerals are mixed evenly throughout the
rock.
C. Pure compound, because the granite and quartz are chemically bonded together.
D. Pure element, because the sample consists entirely of naturally occurring earth
materials.
Correct Answer: A
Rationale: A heterogeneous mixture contains physically distinct parts that are not
uniformly distributed, such as veins of quartz in granite. A tempting wrong answer
classifies it as a homogeneous mixture, which would require the components to be
evenly distributed and indistinguishable. For the exam, if you can see distinct
pieces, it is heterogeneous.
Question 4 of 50
, 4
An environmental chemist needs to convert a water contaminant measurement
from 45 micrograms per liter to milligrams per liter for a regulatory report.
A. 0.045 mg/L
B. 4.5 mg/L
C. 0.045 mg/L
D. 0.045 mg/L ✓ CORRECT
Correct Answer: D
Rationale: Converting micrograms to milligrams requires dividing by 1,000,
moving the decimal three places to the left. The trap of 4.5 mg/L results from
incorrectly multiplying by 1,000 instead of dividing. Memorizing that milli- is
larger than micro- prevents this inversion.
Question 5 of 50
A materials scientist is tasked with identifying an unknown metal cube. The cube
has a volume of 12.5 cm³ and a mass of 52.75 g. The scientist needs to calculate
the density to compare it against known standards.
A. 0.237 g/cm³
B. 4.22 g/cm³ ✓ CORRECT
C. 65.25 g/cm³
D. 4220 g/cm³
Correct Answer: B
