WGU D425 Intro to Chemistry Exam Questions
and Answers (2026) | Comprehensive Review
with Detailed Rationales | A+ Verified
• How do you distinguish between a pure substance and a mixture? -✓✓A pure
substance has a fixed chemical composition throughout, while a mixture consists
of two or more substances physically combined with variable composition.
• What is the difference between an intensive and extensive property? -
✓✓Intensive properties (e.g., density, boiling point) are independent of the amount
of matter; extensive properties (e.g., mass, volume) depend on the amount of
matter present.
• How do you determine the state of matter based on temperature relative to
melting and boiling points? -✓✓If T < melting point, it is a solid. If melting point
< T < boiling point, it is a liquid. If T > boiling point, it is a gas.
• What are the rules for significant figures in multiplication and division? -✓✓The
final answer must have the same number of significant figures as the measurement
with the fewest significant figures.
• How do you calculate density? -✓✓Density = mass / volume. For irregular
objects, volume can be found via water displacement.
• What is the charge, location, and relative mass of a proton? -✓✓Positive charge
(+1), located in the nucleus, relative mass of approximately 1 atomic mass unit
(amu).
, • What defines an isotope? -✓✓Atoms of the same element (same number of
protons) that have different numbers of neutrons, resulting in different mass
numbers.
• What is the periodic trend for electronegativity? -✓✓Electronegativity increases
from left to right across a period and decreases down a group.
• How do you calculate average atomic mass? -✓✓Multiply the mass of each
isotope by its relative abundance (as a decimal) and sum the results.
• What is the difference between ionic and covalent bonding? -✓✓Ionic bonds
involve the transfer of electrons between a metal and a non-metal; covalent bonds
involve the sharing of electrons between two non-metals.
• What is the VSEPR theory used for? -✓✓Predicting the 3D molecular geometry
of a molecule based on the repulsion between electron pairs surrounding a central
atom.
• How do you convert between moles and particles (atoms/molecules)? -✓✓Use
Avogadro's number: 1 mole = 6.022 x 10^23 particles.
• What is the definition of a limiting reactant? -✓✓The reactant that is completely
consumed in a chemical reaction, thereby limiting the amount of product that can
be formed.
• How do you calculate percent yield? -✓✓Percent Yield = (Actual Yield /
Theoretical Yield) x 100%.
and Answers (2026) | Comprehensive Review
with Detailed Rationales | A+ Verified
• How do you distinguish between a pure substance and a mixture? -✓✓A pure
substance has a fixed chemical composition throughout, while a mixture consists
of two or more substances physically combined with variable composition.
• What is the difference between an intensive and extensive property? -
✓✓Intensive properties (e.g., density, boiling point) are independent of the amount
of matter; extensive properties (e.g., mass, volume) depend on the amount of
matter present.
• How do you determine the state of matter based on temperature relative to
melting and boiling points? -✓✓If T < melting point, it is a solid. If melting point
< T < boiling point, it is a liquid. If T > boiling point, it is a gas.
• What are the rules for significant figures in multiplication and division? -✓✓The
final answer must have the same number of significant figures as the measurement
with the fewest significant figures.
• How do you calculate density? -✓✓Density = mass / volume. For irregular
objects, volume can be found via water displacement.
• What is the charge, location, and relative mass of a proton? -✓✓Positive charge
(+1), located in the nucleus, relative mass of approximately 1 atomic mass unit
(amu).
, • What defines an isotope? -✓✓Atoms of the same element (same number of
protons) that have different numbers of neutrons, resulting in different mass
numbers.
• What is the periodic trend for electronegativity? -✓✓Electronegativity increases
from left to right across a period and decreases down a group.
• How do you calculate average atomic mass? -✓✓Multiply the mass of each
isotope by its relative abundance (as a decimal) and sum the results.
• What is the difference between ionic and covalent bonding? -✓✓Ionic bonds
involve the transfer of electrons between a metal and a non-metal; covalent bonds
involve the sharing of electrons between two non-metals.
• What is the VSEPR theory used for? -✓✓Predicting the 3D molecular geometry
of a molecule based on the repulsion between electron pairs surrounding a central
atom.
• How do you convert between moles and particles (atoms/molecules)? -✓✓Use
Avogadro's number: 1 mole = 6.022 x 10^23 particles.
• What is the definition of a limiting reactant? -✓✓The reactant that is completely
consumed in a chemical reaction, thereby limiting the amount of product that can
be formed.
• How do you calculate percent yield? -✓✓Percent Yield = (Actual Yield /
Theoretical Yield) x 100%.
