2026 UPDATED QUESTIONS DOWNLOAD
WGU D425 Introduction to Chemistry: Comprehensive 450+-Question
Exam Prep
This high-yield study guide provides a massive bank of 400+ practice questions
specifically designed to align with the WGU D425 Objective Assessment. It covers
every critical competency, including atomic structure, chemical bonding, stoichiometry,
gas laws, and acids/bases. Each question features a bolded correct answer and a
detailed italicized rationale to help you master the "why" behind the chemistry,
ensuring you are fully prepared for your proctored exam.
1. Which subatomic particle determines the identity of an element?
A. Electron
B. Neutron
C. Proton
D. Photon
Rationale: The number of protons (atomic number) is unique to each element. Changing the
number of protons changes the element itself.
2. An atom of Carbon-14 has how many neutrons?
A. 6
B. 8
C. 14
D. 12
Rationale: Carbon always has 6 protons. The mass number (14) minus the atomic number (6)
equals 8 neutrons.
3. Which of the following is a physical change?
A. Wood burning
B. Iron rusting
C. Ice melting
D. An antacid neutralizing stomach acid
Rationale: Physical changes do not change the chemical identity of a substance. Melting is a
change of state, while the others are chemical reactions.
4. Which group on the periodic table is known as the Halogens?
A. Group 1
B. Group 2
C. Group 18
D. Group 17
, 2026 UPDATED QUESTIONS DOWNLOAD
Rationale: Group 17 elements (F, Cl, Br, I, At) are highly reactive nonmetals known as
Halogens.
5. What is the trend for electronegativity on the periodic table?
A. Increases down and to the left
B. Increases up and to the right
C. Decreases up and to the right
D. Remains constant across a period
Rationale: Electronegativity increases as you move toward Fluorine, which is the most
electronegative element.
6. Which type of bond involves the sharing of electrons between two nonmetals?
A. Ionic
B. Covalent
C. Metallic
D. Hydrogen
Rationale: Covalent bonds occur when atoms share electron pairs. Ionic bonds involve the
transfer of electrons from a metal to a nonmetal.
7. What is the molar mass of Water (
)? (H=1.01 g/mol, O=16.00 g/mol)
A. 17.01 g/mol
B. 18.02 g/mol
C. 16.00 g/mol
D. 32.00 g/mol
Rationale: (2 x 1.01) + 16.00 = 18.02 g/mol.
8. According to VSEPR theory, what is the shape of a
molecule?
A. Linear
B. Bent
C. Tetrahedral
D. Trigonal planar
Rationale: Methane has four bonding pairs and zero lone pairs around the central carbon atom,
resulting in a tetrahedral geometry.
9. Which state of matter has a definite volume but takes the shape of its container?
A. Solid
B. Liquid
C. Gas
D. Plasma
, 2026 UPDATED QUESTIONS DOWNLOAD
Rationale: Liquids have particles close together (definite volume) but can slide past one
another (indefinite shape).
10. How many valence electrons does an atom of Oxygen have?
A. 2
B. 4
C. 6
D. 8
Rationale: Oxygen is in Group 16, meaning it has 6 electrons in its outermost shell.
11. Which law states that matter cannot be created or destroyed in a chemical reaction?
A. Law of Multiple Proportions
B. Law of Conservation of Mass
C. Avogadro's Law
D. Boyle's Law
Rationale: This law requires that chemical equations be balanced so the number of atoms of
each element is the same on both sides.
12. What is the charge of a Magnesium ion?
A. +1
B. +2
C. -1
D. -2
Rationale: Magnesium is an Alkaline Earth Metal (Group 2) and loses two electrons to achieve
a stable octet.
13. In the reaction
, what is the mole ratio of
to
?
A. 1:1
B. 2:2 (or 1:1)
C. 2:1
D. 1:2
Rationale: The coefficients in front of the molecules indicate the molar ratio (2 moles of
hydrogen produce 2 moles of water).
14. Which of the following is a homogeneous mixture?
A. Salad dressing
B. Saltwater
, 2026 UPDATED QUESTIONS DOWNLOAD
C. Chocolate chip cookies
D. Trail mix
Rationale: Homogeneous mixtures (solutions) have a uniform composition throughout.
15. What is the density of a substance with a mass of 20g and a volume of 5mL?
A. 100 g/mL
B. 0.25 g/mL
C. 4 g/mL
D. 15 g/mL
Rationale: Density = Mass / Volume. 20g / 5mL = 4 g/mL.
16. Which element has the largest atomic radius?
A. Fluorine (F)
B. Francium (Fr)
C. Lithium (Li)
D. Neon (Ne)
Rationale: Atomic radius increases as you move down a group and to the left across a period.
17. What is the correct formula for Sodium Chloride?
A.
B.
C.
D.
Rationale:
has a +1 charge and
has a -1 charge, so they combine in a 1:1 ratio.
18. An isotope has the same number of protons but a different number of:
A. Electrons
B. Neutrons
C. Protons
D. Positrons
WGU D425 Introduction to Chemistry: Comprehensive 450+-Question
Exam Prep
This high-yield study guide provides a massive bank of 400+ practice questions
specifically designed to align with the WGU D425 Objective Assessment. It covers
every critical competency, including atomic structure, chemical bonding, stoichiometry,
gas laws, and acids/bases. Each question features a bolded correct answer and a
detailed italicized rationale to help you master the "why" behind the chemistry,
ensuring you are fully prepared for your proctored exam.
1. Which subatomic particle determines the identity of an element?
A. Electron
B. Neutron
C. Proton
D. Photon
Rationale: The number of protons (atomic number) is unique to each element. Changing the
number of protons changes the element itself.
2. An atom of Carbon-14 has how many neutrons?
A. 6
B. 8
C. 14
D. 12
Rationale: Carbon always has 6 protons. The mass number (14) minus the atomic number (6)
equals 8 neutrons.
3. Which of the following is a physical change?
A. Wood burning
B. Iron rusting
C. Ice melting
D. An antacid neutralizing stomach acid
Rationale: Physical changes do not change the chemical identity of a substance. Melting is a
change of state, while the others are chemical reactions.
4. Which group on the periodic table is known as the Halogens?
A. Group 1
B. Group 2
C. Group 18
D. Group 17
, 2026 UPDATED QUESTIONS DOWNLOAD
Rationale: Group 17 elements (F, Cl, Br, I, At) are highly reactive nonmetals known as
Halogens.
5. What is the trend for electronegativity on the periodic table?
A. Increases down and to the left
B. Increases up and to the right
C. Decreases up and to the right
D. Remains constant across a period
Rationale: Electronegativity increases as you move toward Fluorine, which is the most
electronegative element.
6. Which type of bond involves the sharing of electrons between two nonmetals?
A. Ionic
B. Covalent
C. Metallic
D. Hydrogen
Rationale: Covalent bonds occur when atoms share electron pairs. Ionic bonds involve the
transfer of electrons from a metal to a nonmetal.
7. What is the molar mass of Water (
)? (H=1.01 g/mol, O=16.00 g/mol)
A. 17.01 g/mol
B. 18.02 g/mol
C. 16.00 g/mol
D. 32.00 g/mol
Rationale: (2 x 1.01) + 16.00 = 18.02 g/mol.
8. According to VSEPR theory, what is the shape of a
molecule?
A. Linear
B. Bent
C. Tetrahedral
D. Trigonal planar
Rationale: Methane has four bonding pairs and zero lone pairs around the central carbon atom,
resulting in a tetrahedral geometry.
9. Which state of matter has a definite volume but takes the shape of its container?
A. Solid
B. Liquid
C. Gas
D. Plasma
, 2026 UPDATED QUESTIONS DOWNLOAD
Rationale: Liquids have particles close together (definite volume) but can slide past one
another (indefinite shape).
10. How many valence electrons does an atom of Oxygen have?
A. 2
B. 4
C. 6
D. 8
Rationale: Oxygen is in Group 16, meaning it has 6 electrons in its outermost shell.
11. Which law states that matter cannot be created or destroyed in a chemical reaction?
A. Law of Multiple Proportions
B. Law of Conservation of Mass
C. Avogadro's Law
D. Boyle's Law
Rationale: This law requires that chemical equations be balanced so the number of atoms of
each element is the same on both sides.
12. What is the charge of a Magnesium ion?
A. +1
B. +2
C. -1
D. -2
Rationale: Magnesium is an Alkaline Earth Metal (Group 2) and loses two electrons to achieve
a stable octet.
13. In the reaction
, what is the mole ratio of
to
?
A. 1:1
B. 2:2 (or 1:1)
C. 2:1
D. 1:2
Rationale: The coefficients in front of the molecules indicate the molar ratio (2 moles of
hydrogen produce 2 moles of water).
14. Which of the following is a homogeneous mixture?
A. Salad dressing
B. Saltwater
, 2026 UPDATED QUESTIONS DOWNLOAD
C. Chocolate chip cookies
D. Trail mix
Rationale: Homogeneous mixtures (solutions) have a uniform composition throughout.
15. What is the density of a substance with a mass of 20g and a volume of 5mL?
A. 100 g/mL
B. 0.25 g/mL
C. 4 g/mL
D. 15 g/mL
Rationale: Density = Mass / Volume. 20g / 5mL = 4 g/mL.
16. Which element has the largest atomic radius?
A. Fluorine (F)
B. Francium (Fr)
C. Lithium (Li)
D. Neon (Ne)
Rationale: Atomic radius increases as you move down a group and to the left across a period.
17. What is the correct formula for Sodium Chloride?
A.
B.
C.
D.
Rationale:
has a +1 charge and
has a -1 charge, so they combine in a 1:1 ratio.
18. An isotope has the same number of protons but a different number of:
A. Electrons
B. Neutrons
C. Protons
D. Positrons
