WGU D425 Intro to Chemistry Questions
and Answers (2026/2027) | Updated
Review | A+ Verified
• What is the difference between an intensive and extensive property? CORRECT
ANSWER: 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? CORRECT ANSWER: 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? CORRECT
ANSWER: The final answer must have the same number of significant figures as the
measurement with the fewest significant figures.
• How do you calculate density? CORRECT ANSWER: Density = mass / volume. For
irregular objects, volume can be found via water displacement.
• What is the charge, location, and relative mass of a proton? CORRECT ANSWER:
Positive charge (+1), located in the nucleus, relative mass of approximately 1 atomic
mass unit (amu).
• What defines an isotope? CORRECT ANSWER: 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? CORRECT ANSWER:
Electronegativity increases from left to right across a period and decreases down a
group.
• How do you calculate average atomic mass? CORRECT ANSWER: 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? CORRECT ANSWER:
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? CORRECT ANSWER: 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)? CORRECT
ANSWER: Use Avogadro's number: 1 mole = 6.022 x 10^23 particles.
• What is the definition of a limiting reactant? CORRECT ANSWER: 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? CORRECT ANSWER: Percent Yield = (Actual
Yield / Theoretical Yield) x 100%.
• What occurs in a redox reaction? CORRECT ANSWER: The transfer of electrons
between species; one substance is oxidized (loses electrons) and another is reduced
(gains electrons).
• What is the difference between a physical and chemical change? CORRECT
ANSWER: A physical change alters the form or state of matter without changing its
chemical identity; a chemical change results in the formation of new substances.
• How do you identify a direct relationship on a graph? CORRECT ANSWER: A direct
relationship shows a straight line passing through the origin (y = kx).
• What is the base SI unit for mass? CORRECT ANSWER: The kilogram (kg).
• How many valence electrons does an element in Group 17 have? CORRECT
ANSWER: 7 valence electrons.
• What is the formula for calculating percent composition? CORRECT ANSWER: (Mass
of element in formula / Molar mass of compound) x 100%.
• What is the purpose of balancing a chemical equation? CORRECT ANSWER: To
satisfy the Law of Conservation of Mass, ensuring the number of atoms of each element
is the same on both sides of the reaction.
• What is the volume of one mole of any gas at STP? CORRECT ANSWER: 22.4 liters.
• How do you identify an oxidizing agent? CORRECT ANSWER: The oxidizing agent is
the substance that gets reduced (gains electrons).
• What is the trend for atomic radius on the periodic table? CORRECT ANSWER:
Atomic radius decreases from left to right across a period and increases down a group.
• How do you determine the charge of an ion for a main-group element? CORRECT
ANSWER: Use the group number: metals lose electrons to form positive cations, non-
metals gain electrons to form negative anions.
and Answers (2026/2027) | Updated
Review | A+ Verified
• What is the difference between an intensive and extensive property? CORRECT
ANSWER: 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? CORRECT ANSWER: 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? CORRECT
ANSWER: The final answer must have the same number of significant figures as the
measurement with the fewest significant figures.
• How do you calculate density? CORRECT ANSWER: Density = mass / volume. For
irregular objects, volume can be found via water displacement.
• What is the charge, location, and relative mass of a proton? CORRECT ANSWER:
Positive charge (+1), located in the nucleus, relative mass of approximately 1 atomic
mass unit (amu).
• What defines an isotope? CORRECT ANSWER: 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? CORRECT ANSWER:
Electronegativity increases from left to right across a period and decreases down a
group.
• How do you calculate average atomic mass? CORRECT ANSWER: 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? CORRECT ANSWER:
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? CORRECT ANSWER: 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)? CORRECT
ANSWER: Use Avogadro's number: 1 mole = 6.022 x 10^23 particles.
• What is the definition of a limiting reactant? CORRECT ANSWER: 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? CORRECT ANSWER: Percent Yield = (Actual
Yield / Theoretical Yield) x 100%.
• What occurs in a redox reaction? CORRECT ANSWER: The transfer of electrons
between species; one substance is oxidized (loses electrons) and another is reduced
(gains electrons).
• What is the difference between a physical and chemical change? CORRECT
ANSWER: A physical change alters the form or state of matter without changing its
chemical identity; a chemical change results in the formation of new substances.
• How do you identify a direct relationship on a graph? CORRECT ANSWER: A direct
relationship shows a straight line passing through the origin (y = kx).
• What is the base SI unit for mass? CORRECT ANSWER: The kilogram (kg).
• How many valence electrons does an element in Group 17 have? CORRECT
ANSWER: 7 valence electrons.
• What is the formula for calculating percent composition? CORRECT ANSWER: (Mass
of element in formula / Molar mass of compound) x 100%.
• What is the purpose of balancing a chemical equation? CORRECT ANSWER: To
satisfy the Law of Conservation of Mass, ensuring the number of atoms of each element
is the same on both sides of the reaction.
• What is the volume of one mole of any gas at STP? CORRECT ANSWER: 22.4 liters.
• How do you identify an oxidizing agent? CORRECT ANSWER: The oxidizing agent is
the substance that gets reduced (gains electrons).
• What is the trend for atomic radius on the periodic table? CORRECT ANSWER:
Atomic radius decreases from left to right across a period and increases down a group.
• How do you determine the charge of an ion for a main-group element? CORRECT
ANSWER: Use the group number: metals lose electrons to form positive cations, non-
metals gain electrons to form negative anions.
