2026 UPDATED QUESTIONS DOWNLOAD
WGU D425 Introduction to Chemistry OA Exam Prep – High-Yield Practice Questions &
Rationales 2026
This comprehensive study resource features 250+ expert-verified practice questions designed
specifically for the WGU D425 Objective Assessment. Covering everything from periodic trends and
chemical bonding to stoichiometry and gas laws, each question includes a bolded answer for quick
self-testing and a detailed italicized rationale to ensure a deep understanding of core chemistry
concepts. It is an essential tool for WGU students looking to identify knowledge gaps, master the math-
heavy modules, and pass the OA on the first attempt.
1. Mercury has a freezing point of
and a boiling point of
. Which state will mercury be in at
?
A. Gas
B. Liquid
C. Plasma
D. Solid
Answer: B. Liquid
Rationale: Since
is above the freezing point (
) but below the boiling point (
), the substance exists in the liquid phase.
2. What is the atomic number of an atom that contains 58 protons, 58 electrons, and 82
neutrons?
A. 58
B. 82
C. 116
D. 140
, 2026 UPDATED QUESTIONS DOWNLOAD
Answer: A. 58
Rationale: The atomic number of an element is defined strictly as the total number of protons in
its nucleus.
3. Which subatomic particle has a negative charge?
A. Proton
B. Neutron
C. Electron
D. Nucleus
Answer: C. Electron
Rationale: Electrons are the negatively charged subatomic particles that orbit the nucleus;
protons are positive and neutrons are neutral.
4. A beverage is made by mixing sugar, water, and freshly squeezed lemon juice
(without pulp) until uniform. This is categorized as a:
A. Compound
B. Element
C. Heterogeneous mixture
D. Homogeneous mixture
Answer: D. Homogeneous mixture
Rationale: A homogeneous mixture is uniform throughout, meaning any sample taken will have
the same composition.
5. Which of the following is an example of an extensive property?
A. Density
B. Temperature
C. Mass
D. Color
Answer: C. Mass
Rationale: Extensive properties depend on the amount of matter present (e.g., mass, volume).
Intensive properties do not change with the amount (e.g., density, conductivity).
6. How many valence electrons do the Halogens (Group 17) have?
A. 1
B. 2
C. 7
D. 8
Answer: C. 7
Rationale: Elements in the Halogen family (Group 17) all possess 7 valence electrons in their
outermost shell.
7. Which type of bond involves the transfer of electrons between a metal and a
nonmetal?
, 2026 UPDATED QUESTIONS DOWNLOAD
A. Covalent
B. Ionic
C. Metallic
D. Hydrogen
Answer: B. Ionic
Rationale: Ionic bonds are formed by the electrostatic attraction between ions created when a
metal transfers electrons to a nonmetal.
Quizlet +1
8. What is the correct name for the compound
?
A. Strontium Chloride
B. Strontium Dichloride
C. Distrontium Chloride
D. Strontium Chlorine
Answer: A. Strontium Chloride
Rationale: For ionic compounds involving a main-group metal, the name of the metal is
followed by the nonmetal ending in "-ide" without prefixes.
9. In a covalent bond, electrons are:
A. Transferred
B. Shared
C. Lost
D. Gained
Answer: B. Shared
Rationale: Covalent bonds are formed when two nonmetal atoms share one or more pairs of
electrons.
Quizlet +1
10. What is the approximate bond angle for a molecule with tetrahedral electron pair
geometry?
A.
B.
C.
, 2026 UPDATED QUESTIONS DOWNLOAD
D.
Answer: B.
Rationale: In a tetrahedral arrangement, the four pairs of electrons repel each other equally,
resulting in an angle of
degrees.
11. A sample contains 75% Carbon-12 and 25% Carbon-14. What is the average atomic
mass?
A. 12.0 amu
B. 12.5 amu
C. 13.0 amu
D. 14.0 amu
Answer: B. 12.5 amu
Rationale:
amu.
12. What type of reaction is
?
A. Decomposition
B. Synthesis (Combination)
C. Single-replacement
D. Double-replacement
WGU D425 Introduction to Chemistry OA Exam Prep – High-Yield Practice Questions &
Rationales 2026
This comprehensive study resource features 250+ expert-verified practice questions designed
specifically for the WGU D425 Objective Assessment. Covering everything from periodic trends and
chemical bonding to stoichiometry and gas laws, each question includes a bolded answer for quick
self-testing and a detailed italicized rationale to ensure a deep understanding of core chemistry
concepts. It is an essential tool for WGU students looking to identify knowledge gaps, master the math-
heavy modules, and pass the OA on the first attempt.
1. Mercury has a freezing point of
and a boiling point of
. Which state will mercury be in at
?
A. Gas
B. Liquid
C. Plasma
D. Solid
Answer: B. Liquid
Rationale: Since
is above the freezing point (
) but below the boiling point (
), the substance exists in the liquid phase.
2. What is the atomic number of an atom that contains 58 protons, 58 electrons, and 82
neutrons?
A. 58
B. 82
C. 116
D. 140
, 2026 UPDATED QUESTIONS DOWNLOAD
Answer: A. 58
Rationale: The atomic number of an element is defined strictly as the total number of protons in
its nucleus.
3. Which subatomic particle has a negative charge?
A. Proton
B. Neutron
C. Electron
D. Nucleus
Answer: C. Electron
Rationale: Electrons are the negatively charged subatomic particles that orbit the nucleus;
protons are positive and neutrons are neutral.
4. A beverage is made by mixing sugar, water, and freshly squeezed lemon juice
(without pulp) until uniform. This is categorized as a:
A. Compound
B. Element
C. Heterogeneous mixture
D. Homogeneous mixture
Answer: D. Homogeneous mixture
Rationale: A homogeneous mixture is uniform throughout, meaning any sample taken will have
the same composition.
5. Which of the following is an example of an extensive property?
A. Density
B. Temperature
C. Mass
D. Color
Answer: C. Mass
Rationale: Extensive properties depend on the amount of matter present (e.g., mass, volume).
Intensive properties do not change with the amount (e.g., density, conductivity).
6. How many valence electrons do the Halogens (Group 17) have?
A. 1
B. 2
C. 7
D. 8
Answer: C. 7
Rationale: Elements in the Halogen family (Group 17) all possess 7 valence electrons in their
outermost shell.
7. Which type of bond involves the transfer of electrons between a metal and a
nonmetal?
, 2026 UPDATED QUESTIONS DOWNLOAD
A. Covalent
B. Ionic
C. Metallic
D. Hydrogen
Answer: B. Ionic
Rationale: Ionic bonds are formed by the electrostatic attraction between ions created when a
metal transfers electrons to a nonmetal.
Quizlet +1
8. What is the correct name for the compound
?
A. Strontium Chloride
B. Strontium Dichloride
C. Distrontium Chloride
D. Strontium Chlorine
Answer: A. Strontium Chloride
Rationale: For ionic compounds involving a main-group metal, the name of the metal is
followed by the nonmetal ending in "-ide" without prefixes.
9. In a covalent bond, electrons are:
A. Transferred
B. Shared
C. Lost
D. Gained
Answer: B. Shared
Rationale: Covalent bonds are formed when two nonmetal atoms share one or more pairs of
electrons.
Quizlet +1
10. What is the approximate bond angle for a molecule with tetrahedral electron pair
geometry?
A.
B.
C.
, 2026 UPDATED QUESTIONS DOWNLOAD
D.
Answer: B.
Rationale: In a tetrahedral arrangement, the four pairs of electrons repel each other equally,
resulting in an angle of
degrees.
11. A sample contains 75% Carbon-12 and 25% Carbon-14. What is the average atomic
mass?
A. 12.0 amu
B. 12.5 amu
C. 13.0 amu
D. 14.0 amu
Answer: B. 12.5 amu
Rationale:
amu.
12. What type of reaction is
?
A. Decomposition
B. Synthesis (Combination)
C. Single-replacement
D. Double-replacement
