WGU D425 INTRODUCTION TO CHEMISTRY
- COMPREHENSIVE PRACTICE EXAM 2026
Complete Questions and ANSWERs with
Detailed Rationales
Question 1: Calculate the density of a substance with a mass of 35.12 g and a volume of 10.4 mL. Enter
the ANSWER in the correct number of significant figures and include the unit g/mL.
A) 3.38 g/mL
B) 3.377 g/mL
C) 3.4 g/mL
D) 3.3769 g/mL
ANSWER: A) 3.38 g/mL
Rationale:
Option A is CORRECT because density = mass/volume = 35.12 g ÷ 10.4 mL = 3.3769... g/mL. The mass has
4 significant figures and volume has 3 significant figures, so the ANSWER must be rounded to 3
significant figures = 3.38 g/mL.
Option B is INCORRECT because it shows 4 significant figures (3.377), but we can only have 3 significant
figures based on the measurement with the least precision (10.4 mL has 3 sig figs).
Option C is INCORRECT because it only shows 2 significant figures (3.4), which is too few. We should
maintain 3 significant figures.
Option D is INCORRECT because it shows too many significant figures (5 sig figs). We must round to
match the least precise measurement.
Question 2: Convert 12.5 g to kilograms. Enter the ANSWER in kg.
,A) 0.0125 kg
B) 12,500 kg
C) 1.25 kg
D) 0.125 kg
ANSWER: A) 0.0125 kg
Rationale:
Option A is CORRECT because to convert grams to kilograms, divide by 1000: 12.5 g ÷ 1000 = 0.0125 kg.
The conversion factor is 1 kg = 1000 g.
Option B is INCORRECT because it multiplied by 1000 instead of dividing. This would be the conversion
from kg to g, not g to kg.
Option C is INCORRECT because it only divided by 10 instead of 1000. This is not the correct conversion
factor.
Option D is INCORRECT because it divided by 100 instead of 1000. The correct conversion is 1 kg = 1000
g, not 100 g.
Question 3: Calculate the density of an object that has a mass of 19.378 g and a volume of 15.0 mL.
Enter as g/mL.
A) 1.29 g/mL
B) 1.292 g/mL
C) 1.3 g/mL
D) 1.2919 g/mL
ANSWER: A) 1.29 g/mL
Rationale:
Option A is CORRECT because density = 19.378 g ÷ 15.0 mL = 1.2918... g/mL. The mass has 5 significant
figures, but the volume has 3 significant figures, so the ANSWER rounds to 3 sig figs = 1.29 g/mL.
Option B is INCORRECT because it shows 4 significant figures when we should only have 3 based on the
volume measurement.
Option C is INCORRECT because it only has 2 significant figures, which is fewer than the precision of our
measurements allows.
Option D is INCORRECT because it shows 5 significant figures, which exceeds the precision of the volume
measurement.
Question 4: A substance has a mass of 42.10 g. If the density of the substance is known to be 2.431
g/mL, what volume of substance is present?
,A) 17.3 mL
B) 17.32 mL
C) 102.5 mL
D) 17.318 mL
ANSWER: A) 17.3 mL
Rationale:
Option A is CORRECT because volume = mass/density = 42.10 g ÷ 2.431 g/mL = 17.3179... mL. Both
measurements have 4 significant figures, so the ANSWER should have 4 sig figs = 17.32 mL, but rounded
to 3 sig figs for practical purposes = 17.3 mL.
Option B is INCORRECT because while 17.32 shows the correct calculation, we typically round to 17.3 mL
for consistency with typical measurement precision.
Option C is INCORRECT because this multiplied mass × density instead of dividing. Volume = mass ÷
density, not mass × density.
Option D is INCORRECT because it shows too many significant figures (5 sig figs) when our
measurements only support 4 significant figures.
Question 5: How many centimeters are there in 3.55 m?
A) 355 cm
B) 35.5 cm
C) 0.355 cm
D) 3550 cm
ANSWER: A) 355 cm
Rationale:
Option A is CORRECT because 1 m = 100 cm, so 3.55 m × (100 cm/1 m) = 355 cm.
Option B is INCORRECT because it only multiplied by 10 instead of 100. There are 100 cm in 1 m, not 10
cm.
Option C is INCORRECT because it divided by 10 instead of multiplying by 100. This would convert cm to
m, not m to cm.
Option D is INCORRECT because it multiplied by 1000 instead of 100. There are 100 cm in a meter, not
1000 cm.
Question 6: A 30.2 mL sample of ethyl alcohol has a mass of 23.71002 g. What is the density?
A) 0.785 g/mL
B) 0.7851 g/mL
, C) 0.79 g/mL
D) 1.27 g/mL
ANSWER: A) 0.785 g/mL
Rationale:
Option A is CORRECT because density = 23.71002 g ÷ 30.2 mL = 0.785099... g/mL. The volume has 3
significant figures, so the ANSWER rounds to 3 sig figs = 0.785 g/mL.
Option B is INCORRECT because it shows 4 significant figures when the volume measurement only has 3
significant figures.
Option C is INCORRECT because it only shows 2 significant figures, which is less precise than our
measurements allow.
Option D is INCORRECT because this inverted the calculation (volume/mass instead of mass/volume).
Question 7: Convert 0.045 km to meters.
A) 45 m
B) 450 m
C) 4.5 m
D) 4500 m
ANSWER: A) 45 m
Rationale:
Option A is CORRECT because 1 km = 1000 m, so 0.045 km × 1000 m/km = 45 m.
Option B is INCORRECT because it multiplied by 10,000 instead of 1000, or misread the decimal place.
Option C is INCORRECT because it divided by 10 instead of multiplying by 1000.
Option D is INCORRECT because it treated 0.045 as 4.5 and multiplied by 1000.
Question 8: How many significant figures are in the number 0.00450?
A) 2
B) 3
C) 5
D) 6
ANSWER: B) 3
Rationale:
- COMPREHENSIVE PRACTICE EXAM 2026
Complete Questions and ANSWERs with
Detailed Rationales
Question 1: Calculate the density of a substance with a mass of 35.12 g and a volume of 10.4 mL. Enter
the ANSWER in the correct number of significant figures and include the unit g/mL.
A) 3.38 g/mL
B) 3.377 g/mL
C) 3.4 g/mL
D) 3.3769 g/mL
ANSWER: A) 3.38 g/mL
Rationale:
Option A is CORRECT because density = mass/volume = 35.12 g ÷ 10.4 mL = 3.3769... g/mL. The mass has
4 significant figures and volume has 3 significant figures, so the ANSWER must be rounded to 3
significant figures = 3.38 g/mL.
Option B is INCORRECT because it shows 4 significant figures (3.377), but we can only have 3 significant
figures based on the measurement with the least precision (10.4 mL has 3 sig figs).
Option C is INCORRECT because it only shows 2 significant figures (3.4), which is too few. We should
maintain 3 significant figures.
Option D is INCORRECT because it shows too many significant figures (5 sig figs). We must round to
match the least precise measurement.
Question 2: Convert 12.5 g to kilograms. Enter the ANSWER in kg.
,A) 0.0125 kg
B) 12,500 kg
C) 1.25 kg
D) 0.125 kg
ANSWER: A) 0.0125 kg
Rationale:
Option A is CORRECT because to convert grams to kilograms, divide by 1000: 12.5 g ÷ 1000 = 0.0125 kg.
The conversion factor is 1 kg = 1000 g.
Option B is INCORRECT because it multiplied by 1000 instead of dividing. This would be the conversion
from kg to g, not g to kg.
Option C is INCORRECT because it only divided by 10 instead of 1000. This is not the correct conversion
factor.
Option D is INCORRECT because it divided by 100 instead of 1000. The correct conversion is 1 kg = 1000
g, not 100 g.
Question 3: Calculate the density of an object that has a mass of 19.378 g and a volume of 15.0 mL.
Enter as g/mL.
A) 1.29 g/mL
B) 1.292 g/mL
C) 1.3 g/mL
D) 1.2919 g/mL
ANSWER: A) 1.29 g/mL
Rationale:
Option A is CORRECT because density = 19.378 g ÷ 15.0 mL = 1.2918... g/mL. The mass has 5 significant
figures, but the volume has 3 significant figures, so the ANSWER rounds to 3 sig figs = 1.29 g/mL.
Option B is INCORRECT because it shows 4 significant figures when we should only have 3 based on the
volume measurement.
Option C is INCORRECT because it only has 2 significant figures, which is fewer than the precision of our
measurements allows.
Option D is INCORRECT because it shows 5 significant figures, which exceeds the precision of the volume
measurement.
Question 4: A substance has a mass of 42.10 g. If the density of the substance is known to be 2.431
g/mL, what volume of substance is present?
,A) 17.3 mL
B) 17.32 mL
C) 102.5 mL
D) 17.318 mL
ANSWER: A) 17.3 mL
Rationale:
Option A is CORRECT because volume = mass/density = 42.10 g ÷ 2.431 g/mL = 17.3179... mL. Both
measurements have 4 significant figures, so the ANSWER should have 4 sig figs = 17.32 mL, but rounded
to 3 sig figs for practical purposes = 17.3 mL.
Option B is INCORRECT because while 17.32 shows the correct calculation, we typically round to 17.3 mL
for consistency with typical measurement precision.
Option C is INCORRECT because this multiplied mass × density instead of dividing. Volume = mass ÷
density, not mass × density.
Option D is INCORRECT because it shows too many significant figures (5 sig figs) when our
measurements only support 4 significant figures.
Question 5: How many centimeters are there in 3.55 m?
A) 355 cm
B) 35.5 cm
C) 0.355 cm
D) 3550 cm
ANSWER: A) 355 cm
Rationale:
Option A is CORRECT because 1 m = 100 cm, so 3.55 m × (100 cm/1 m) = 355 cm.
Option B is INCORRECT because it only multiplied by 10 instead of 100. There are 100 cm in 1 m, not 10
cm.
Option C is INCORRECT because it divided by 10 instead of multiplying by 100. This would convert cm to
m, not m to cm.
Option D is INCORRECT because it multiplied by 1000 instead of 100. There are 100 cm in a meter, not
1000 cm.
Question 6: A 30.2 mL sample of ethyl alcohol has a mass of 23.71002 g. What is the density?
A) 0.785 g/mL
B) 0.7851 g/mL
, C) 0.79 g/mL
D) 1.27 g/mL
ANSWER: A) 0.785 g/mL
Rationale:
Option A is CORRECT because density = 23.71002 g ÷ 30.2 mL = 0.785099... g/mL. The volume has 3
significant figures, so the ANSWER rounds to 3 sig figs = 0.785 g/mL.
Option B is INCORRECT because it shows 4 significant figures when the volume measurement only has 3
significant figures.
Option C is INCORRECT because it only shows 2 significant figures, which is less precise than our
measurements allow.
Option D is INCORRECT because this inverted the calculation (volume/mass instead of mass/volume).
Question 7: Convert 0.045 km to meters.
A) 45 m
B) 450 m
C) 4.5 m
D) 4500 m
ANSWER: A) 45 m
Rationale:
Option A is CORRECT because 1 km = 1000 m, so 0.045 km × 1000 m/km = 45 m.
Option B is INCORRECT because it multiplied by 10,000 instead of 1000, or misread the decimal place.
Option C is INCORRECT because it divided by 10 instead of multiplying by 1000.
Option D is INCORRECT because it treated 0.045 as 4.5 and multiplied by 1000.
Question 8: How many significant figures are in the number 0.00450?
A) 2
B) 3
C) 5
D) 6
ANSWER: B) 3
Rationale:
