Page 1 of 102
WGU D425 Introduction to Chemistry OA exam COMPLETE
QUESTIONS AND DETAILED SOLUTIONS LATEST UPDATE THIS
YEAR-JUST RELEASED
Summarized Exam Coverage – WGU D425 Introduction to Chemistry OA
The exam covers atomic structure and periodic trends, chemical bonding (ionic, covalent,
polar/nonpolar), molecular geometry and VSEPR theory, stoichiometry and mole calculations, chemical
reactions and balancing equations, gas laws and ideal gas behavior, solutions and concentration
(molarity, percent composition, dilutions), acids and bases (pH, strong/weak, neutralization),
thermochemistry (endothermic/exothermic, enthalpy), equilibrium and Le Chatelier’s principle, and
basic organic chemistry nomenclature.
1. A student measures the mass of a beaker as 25.67 g and then adds a powder, bringing the total to
32.12 g. What is the mass of the powder with correct significant figures?
A) 6.45 g
B) 6.450 g
C) 6.4 g
D) 6.5 g
Answer: A – Subtraction yields 6.45 g, limited by the hundredths place of the original measurements.
2. An atom has 15 protons, 15 electrons, and 16 neutrons. What is its mass number?
A) 15
B) 30
C) 31
, Page 2 of 102
D) 46
Answer: C – Mass number = protons + neutrons = 15 + 16 = 31.
3. Which of the following conversion factors would be used to convert 3.55 meters into centimeters?
A) 1 m/100 cm
B) 100 cm/1 m
C) 1 cm/0.01 m
D) 0.01 m/1 cm
Answer: B – Multiply meters by (100 cm/1 m) to cancel meters.
4. A substance has a mass of 25.92 g and a volume of 74.5 mL. What is its density reported to the correct
significant figures?
A) 0.348 g/mL
B) 0.3479 g/mL
C) 0.35 g/mL
D) 2.87 g/mL
Answer: A – 25.92 ÷ 74.5 = 0.3479, rounded to 0.348 g/mL with 3 significant figures.
, Page 3 of 102
5. The density of titanium is 4.51 g/cm³. What is the mass in grams of 10.0 cm³ of titanium?
A) 0.451 g
B) 4.51 g
C) 45.1 g
D) 451 g
Answer: C – Mass = density × volume = 4.51 × 10.0 = 45.1 g.
6. How many millimeters are equal to 34.0 meters?
A) 0.034 mm
B) 340 mm
C) 3,400 mm
D) 34,000 mm
Answer: D – Multiply 34.0 × 1000 = 34,000 mm.
7. Which statement describes a pure substance?
A) A combination of two or more elements that can be physically separated
B) A material with constant composition and distinct chemical properties
C) Any mixture that appears uniform throughout
, Page 4 of 102
D) A substance that can be separated by filtration
Answer: B – Pure substances (elements or compounds) have fixed composition.
8. Air is classified as which type of matter?
A) Pure substance
B) Element
C) Compound
D) Homogeneous mixture
Answer: D – Air is a homogeneous mixture of gases, not chemically bonded.
9. Sodium chloride (NaCl) is best described as which of the following?
A) An element
B) A compound
C) A heterogeneous mixture
D) A homogeneous mixture
Answer: B – NaCl is a compound formed by ionic bonds between sodium and chlorine.
WGU D425 Introduction to Chemistry OA exam COMPLETE
QUESTIONS AND DETAILED SOLUTIONS LATEST UPDATE THIS
YEAR-JUST RELEASED
Summarized Exam Coverage – WGU D425 Introduction to Chemistry OA
The exam covers atomic structure and periodic trends, chemical bonding (ionic, covalent,
polar/nonpolar), molecular geometry and VSEPR theory, stoichiometry and mole calculations, chemical
reactions and balancing equations, gas laws and ideal gas behavior, solutions and concentration
(molarity, percent composition, dilutions), acids and bases (pH, strong/weak, neutralization),
thermochemistry (endothermic/exothermic, enthalpy), equilibrium and Le Chatelier’s principle, and
basic organic chemistry nomenclature.
1. A student measures the mass of a beaker as 25.67 g and then adds a powder, bringing the total to
32.12 g. What is the mass of the powder with correct significant figures?
A) 6.45 g
B) 6.450 g
C) 6.4 g
D) 6.5 g
Answer: A – Subtraction yields 6.45 g, limited by the hundredths place of the original measurements.
2. An atom has 15 protons, 15 electrons, and 16 neutrons. What is its mass number?
A) 15
B) 30
C) 31
, Page 2 of 102
D) 46
Answer: C – Mass number = protons + neutrons = 15 + 16 = 31.
3. Which of the following conversion factors would be used to convert 3.55 meters into centimeters?
A) 1 m/100 cm
B) 100 cm/1 m
C) 1 cm/0.01 m
D) 0.01 m/1 cm
Answer: B – Multiply meters by (100 cm/1 m) to cancel meters.
4. A substance has a mass of 25.92 g and a volume of 74.5 mL. What is its density reported to the correct
significant figures?
A) 0.348 g/mL
B) 0.3479 g/mL
C) 0.35 g/mL
D) 2.87 g/mL
Answer: A – 25.92 ÷ 74.5 = 0.3479, rounded to 0.348 g/mL with 3 significant figures.
, Page 3 of 102
5. The density of titanium is 4.51 g/cm³. What is the mass in grams of 10.0 cm³ of titanium?
A) 0.451 g
B) 4.51 g
C) 45.1 g
D) 451 g
Answer: C – Mass = density × volume = 4.51 × 10.0 = 45.1 g.
6. How many millimeters are equal to 34.0 meters?
A) 0.034 mm
B) 340 mm
C) 3,400 mm
D) 34,000 mm
Answer: D – Multiply 34.0 × 1000 = 34,000 mm.
7. Which statement describes a pure substance?
A) A combination of two or more elements that can be physically separated
B) A material with constant composition and distinct chemical properties
C) Any mixture that appears uniform throughout
, Page 4 of 102
D) A substance that can be separated by filtration
Answer: B – Pure substances (elements or compounds) have fixed composition.
8. Air is classified as which type of matter?
A) Pure substance
B) Element
C) Compound
D) Homogeneous mixture
Answer: D – Air is a homogeneous mixture of gases, not chemically bonded.
9. Sodium chloride (NaCl) is best described as which of the following?
A) An element
B) A compound
C) A heterogeneous mixture
D) A homogeneous mixture
Answer: B – NaCl is a compound formed by ionic bonds between sodium and chlorine.
