200+ QUESTIONS & ANSWERS WITH
RATIONALES
, WGU D425 INTRO TO CHEMISTRY MIDTERM EXAM 2026/2027 | PRACTICE QUESTIONS &
ANSWERS WITH RATIONALES
SECTION 1: MEASUREMENT, SIGNIFICANT FIGURES, AND DENSITY
Question 1
A student measures the mass of an empty 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 the correct number of significant
figures?
A) 6.45 g
B) 6.450 g
C) 6.4 g
D) 6.5 g
Correct Answer: A) 6.45 g
Rationale: The mass of the powder is found by subtracting: 32.12 g - 25.67 g = 6.45 g. The
answer is limited by the hundredths place (two decimal places), which is the least precise
measurement. Both measurements have two decimal places, so the result retains two decimal
places .
Question 2
An irregularly shaped metal object with a mass of 80.4 g is placed in a graduated cylinder
containing 500.5 mL of water. The water level rises to 512.5 mL. What is the density of this
metal?
A) 0.149 g/mL
B) 15.6 g/mL
C) 6.70 g/mL
D) 6.7 g/mL
,Correct Answer: C) 6.70 g/mL
Rationale: The volume of the metal is found by water displacement: 512.5 mL - 500.5 mL = 12.0
mL. Density = mass/volume = 80.4 g / 12.0 mL = 6.70 g/mL. The volume measurement has three
significant figures, so the answer is reported with three significant figures .
Question 3
A substance has a mass of 42.10 g. If the density of the substance is 2.431 g/mL, what volume
of substance is present?
A) 102.4 mL
B) 17.32 mL
C) 44.53 mL
D) 17.3 mL
Correct Answer: B) 17.32 mL
Rationale: Volume is calculated by dividing mass by density: V = m/d = 42.10 g / 2.431 g/mL =
17.32 mL. The answer should be reported with four significant figures to match the least
precise measurement .
Question 4
How many significant figures are in the measurement 0.004050 m?
A) 3
B) 4
C) 5
D) 6
Correct Answer: B) 4
, Rationale: Leading zeros are not significant. The significant digits are 4, 0, 5, 0. The trailing zero
after the decimal point counts as significant. Therefore, there are 4 significant figures .
Question 5
Convert 12.5 grams into kilograms.
A) 1250 kg
B) 0.0125 kg
C) 1.25 kg
D) 125 kg
Correct Answer: B) 0.0125 kg
Rationale: There are 1000 grams in a kilogram. To convert grams to kilograms, divide by 1000:
12.5 g / 1000 = 0.0125 kg. The answer should maintain the same number of significant figures .
SECTION 2: ATOMIC STRUCTURE AND THE PERIODIC TABLE
Question 6
What is the atomic number of an element?
A) The number of neutrons in the nucleus
B) The total mass of the atom
C) The number of protons in the nucleus
D) The number of electrons in the outer shell
E) The sum of protons and neutrons
Correct Answer: C) The number of protons in the nucleus
Rationale: The atomic number uniquely identifies an element and equals the number of
protons in the nucleus. In a neutral atom, it also equals the number of electrons, but atomic
number is defined by the proton count .
RATIONALES
, WGU D425 INTRO TO CHEMISTRY MIDTERM EXAM 2026/2027 | PRACTICE QUESTIONS &
ANSWERS WITH RATIONALES
SECTION 1: MEASUREMENT, SIGNIFICANT FIGURES, AND DENSITY
Question 1
A student measures the mass of an empty 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 the correct number of significant
figures?
A) 6.45 g
B) 6.450 g
C) 6.4 g
D) 6.5 g
Correct Answer: A) 6.45 g
Rationale: The mass of the powder is found by subtracting: 32.12 g - 25.67 g = 6.45 g. The
answer is limited by the hundredths place (two decimal places), which is the least precise
measurement. Both measurements have two decimal places, so the result retains two decimal
places .
Question 2
An irregularly shaped metal object with a mass of 80.4 g is placed in a graduated cylinder
containing 500.5 mL of water. The water level rises to 512.5 mL. What is the density of this
metal?
A) 0.149 g/mL
B) 15.6 g/mL
C) 6.70 g/mL
D) 6.7 g/mL
,Correct Answer: C) 6.70 g/mL
Rationale: The volume of the metal is found by water displacement: 512.5 mL - 500.5 mL = 12.0
mL. Density = mass/volume = 80.4 g / 12.0 mL = 6.70 g/mL. The volume measurement has three
significant figures, so the answer is reported with three significant figures .
Question 3
A substance has a mass of 42.10 g. If the density of the substance is 2.431 g/mL, what volume
of substance is present?
A) 102.4 mL
B) 17.32 mL
C) 44.53 mL
D) 17.3 mL
Correct Answer: B) 17.32 mL
Rationale: Volume is calculated by dividing mass by density: V = m/d = 42.10 g / 2.431 g/mL =
17.32 mL. The answer should be reported with four significant figures to match the least
precise measurement .
Question 4
How many significant figures are in the measurement 0.004050 m?
A) 3
B) 4
C) 5
D) 6
Correct Answer: B) 4
, Rationale: Leading zeros are not significant. The significant digits are 4, 0, 5, 0. The trailing zero
after the decimal point counts as significant. Therefore, there are 4 significant figures .
Question 5
Convert 12.5 grams into kilograms.
A) 1250 kg
B) 0.0125 kg
C) 1.25 kg
D) 125 kg
Correct Answer: B) 0.0125 kg
Rationale: There are 1000 grams in a kilogram. To convert grams to kilograms, divide by 1000:
12.5 g / 1000 = 0.0125 kg. The answer should maintain the same number of significant figures .
SECTION 2: ATOMIC STRUCTURE AND THE PERIODIC TABLE
Question 6
What is the atomic number of an element?
A) The number of neutrons in the nucleus
B) The total mass of the atom
C) The number of protons in the nucleus
D) The number of electrons in the outer shell
E) The sum of protons and neutrons
Correct Answer: C) The number of protons in the nucleus
Rationale: The atomic number uniquely identifies an element and equals the number of
protons in the nucleus. In a neutral atom, it also equals the number of electrons, but atomic
number is defined by the proton count .
