Chem 103 Modules 1-6 Exam Actual
2026/2027 – Complete Exam-Style
Questions | 100% Verified – Pass
Guaranteed – A+ Graded
Content Area Overview
This actual examination reflects the foundational chemical knowledge required for success in Chem 103.
It is designed to evaluate the student's understanding of atomic structure, chemical bonding,
stoichiometry, reactions, and key chemical principles across all six modules. Questions are structured to
assess recall of fundamental concepts, application of chemical formulas and calculations, and analysis of
chemical systems. This authentic question bank represents the real exams used in the course and serves
as a comprehensive resource for students demonstrating mastery of introductory chemistry content.
MODULE 1: Foundations of Chemistry – The Atom
Questions 1–17
Q1. How many significant figures are in the measurement 0.004050 g?
A. 3
B. 4
C. 5
D. 6
Rationale: The best answer is B. Leading zeros (the three zeros before the 4) are not significant—they're
just placeholders. The 4, the 0 after the 4, the 5, and the trailing 0 after the 5 are all significant, giving us
4 significant figures total. The trailing zero after the decimal point is significant because it comes after a
non-zero digit and is to the right of the decimal. This is one of those rules students mix up, so
remember: captive zeros (between non-zero digits) and trailing zeros after the decimal are always
significant.
,Correct Answer: B
Q2. A student measures the mass of a sample as 25.3 g on a balance. This measurement has how many
significant figures?
A. 2
B. 3
C. 4
D. 5
Rationale: The best answer is B. The measurement 25.3 g has three significant figures: the 2, the 5, and
the 3. All non-zero digits are significant, and there's a captive zero between non-zero digits would also
count, but we don't have one here. The decimal point doesn't change the count in this case—it's simply
that all three digits shown are known with certainty based on the precision of the balance used.
Correct Answer: B
Q3. Convert 3.45 × 10⁻³ km to millimeters.
A. 3.45 mm
B. 34.5 mm
C. 345 mm
D. 3450 mm
Rationale: The best answer is D. Starting with 3.45 × 10⁻³ km, we need to convert kilometers to
millimeters. There are 1000 meters in a kilometer and 1000 millimeters in a meter, so there are
1,000,000 mm in a km. Multiplying 3.45 × 10⁻³ by 10¶ gives 3.45 × 10³, which is 3450 mm. A common
trap is stopping at meters (3.45 m) and forgetting the final conversion to millimeters, which is why 3.45
mm and 345 mm show up as distractors.
Correct Answer: D
Q4. An element has an atomic number of 17 and a mass number of 37. How many neutrons does this
atom contain?
A. 17
B. 20
C. 37
D. 54
,Rationale: The best answer is B. The number of neutrons is found by subtracting the atomic number
(number of protons) from the mass number (protons + neutrons). So 37 − 17 = 20 neutrons. The atomic
number tells us this is chlorine, and this particular isotope would be chlorine-37. Students sometimes
confuse atomic number with neutron count or add the two numbers together, which is why 54 shows
up as a distractor.
Correct Answer: B
Q5. Which of the following is the correct number of protons, neutrons, and electrons in a neutral atom
of iron-56 (µ¶Fe)?
A. 26 protons, 26 neutrons, 26 electrons
B. 26 protons, 30 neutrons, 26 electrons
C. 30 protons, 26 neutrons, 30 electrons
D. 56 protons, 26 neutrons, 56 electrons
Rationale: The best answer is B. Iron has an atomic number of 26, so it has 26 protons. In a neutral
atom, the number of electrons equals the number of protons, so 26 electrons. The mass number is 56,
so neutrons = 56 − 26 = 30. The key is remembering that the atomic number (from the periodic table)
gives protons, the mass number is the sum of protons and neutrons, and neutral atoms have equal
protons and electrons. Option A uses the atomic number for neutrons, which is a common error.
Correct Answer: B
Q6. Which element is classified as a metalloid?
A. Sodium (Na)
B. Silicon (Si)
C. Chlorine (Cl)
D. Iron (Fe)
Rationale: The best answer is B. Silicon sits along the staircase line on the periodic table and exhibits
properties intermediate between metals and nonmetals—it's a semiconductor, it has a metallic luster
but is brittle, and it forms covalent network solids. Sodium is a Group 1 alkali metal, chlorine is a halogen
(nonmetal), and iron is a transition metal. The metalloids are B, Si, Ge, As, Sb, Te, and sometimes Po, all
located along the diagonal boundary between metals and nonmetals.
Correct Answer: B
Q7. Which of the following elements is an alkaline earth metal?
, A. Potassium (K)
B. Magnesium (Mg)
C. Aluminum (Al)
D. Argon (Ar)
Rationale: The best answer is B. Magnesium is in Group 2 of the periodic table, which is the alkaline
earth metal group. These elements have two valence electrons and form +2 cations. Potassium is an
alkali metal (Group 1), aluminum is a post-transition metal (Group 13), and argon is a noble gas (Group
18). The group number tells you a lot about an element's properties, so learning the group names pays
off on exams.
Correct Answer: B
Q8. Calculate the average atomic mass of element X given the following isotope data:
Table
Isotope Mass (amu) Natural Abundance
X-10 10.012 19.9%
X-11 11.009 80.1%
A. 10.50 amu
B. 10.81 amu
C. 11.00 amu
D. 21.02 amu
Rationale: The best answer is B. Average atomic mass is a weighted average: (10.012 × 0.199) + (11.009
× 0.801) = 1.992 + 8.818 = 10.81 amu. You multiply each isotope's mass by its fractional abundance and
add the results. A common mistake is simply averaging the two masses without weighting by
abundance, which gives about 10.51, or adding the masses together. This element is boron, by the way,
with an actual average atomic mass of about 10.81 amu.
Correct Answer: B
Q9. How many electrons are in the third energy level (n = 3) of a neutral phosphorus atom?
2026/2027 – Complete Exam-Style
Questions | 100% Verified – Pass
Guaranteed – A+ Graded
Content Area Overview
This actual examination reflects the foundational chemical knowledge required for success in Chem 103.
It is designed to evaluate the student's understanding of atomic structure, chemical bonding,
stoichiometry, reactions, and key chemical principles across all six modules. Questions are structured to
assess recall of fundamental concepts, application of chemical formulas and calculations, and analysis of
chemical systems. This authentic question bank represents the real exams used in the course and serves
as a comprehensive resource for students demonstrating mastery of introductory chemistry content.
MODULE 1: Foundations of Chemistry – The Atom
Questions 1–17
Q1. How many significant figures are in the measurement 0.004050 g?
A. 3
B. 4
C. 5
D. 6
Rationale: The best answer is B. Leading zeros (the three zeros before the 4) are not significant—they're
just placeholders. The 4, the 0 after the 4, the 5, and the trailing 0 after the 5 are all significant, giving us
4 significant figures total. The trailing zero after the decimal point is significant because it comes after a
non-zero digit and is to the right of the decimal. This is one of those rules students mix up, so
remember: captive zeros (between non-zero digits) and trailing zeros after the decimal are always
significant.
,Correct Answer: B
Q2. A student measures the mass of a sample as 25.3 g on a balance. This measurement has how many
significant figures?
A. 2
B. 3
C. 4
D. 5
Rationale: The best answer is B. The measurement 25.3 g has three significant figures: the 2, the 5, and
the 3. All non-zero digits are significant, and there's a captive zero between non-zero digits would also
count, but we don't have one here. The decimal point doesn't change the count in this case—it's simply
that all three digits shown are known with certainty based on the precision of the balance used.
Correct Answer: B
Q3. Convert 3.45 × 10⁻³ km to millimeters.
A. 3.45 mm
B. 34.5 mm
C. 345 mm
D. 3450 mm
Rationale: The best answer is D. Starting with 3.45 × 10⁻³ km, we need to convert kilometers to
millimeters. There are 1000 meters in a kilometer and 1000 millimeters in a meter, so there are
1,000,000 mm in a km. Multiplying 3.45 × 10⁻³ by 10¶ gives 3.45 × 10³, which is 3450 mm. A common
trap is stopping at meters (3.45 m) and forgetting the final conversion to millimeters, which is why 3.45
mm and 345 mm show up as distractors.
Correct Answer: D
Q4. An element has an atomic number of 17 and a mass number of 37. How many neutrons does this
atom contain?
A. 17
B. 20
C. 37
D. 54
,Rationale: The best answer is B. The number of neutrons is found by subtracting the atomic number
(number of protons) from the mass number (protons + neutrons). So 37 − 17 = 20 neutrons. The atomic
number tells us this is chlorine, and this particular isotope would be chlorine-37. Students sometimes
confuse atomic number with neutron count or add the two numbers together, which is why 54 shows
up as a distractor.
Correct Answer: B
Q5. Which of the following is the correct number of protons, neutrons, and electrons in a neutral atom
of iron-56 (µ¶Fe)?
A. 26 protons, 26 neutrons, 26 electrons
B. 26 protons, 30 neutrons, 26 electrons
C. 30 protons, 26 neutrons, 30 electrons
D. 56 protons, 26 neutrons, 56 electrons
Rationale: The best answer is B. Iron has an atomic number of 26, so it has 26 protons. In a neutral
atom, the number of electrons equals the number of protons, so 26 electrons. The mass number is 56,
so neutrons = 56 − 26 = 30. The key is remembering that the atomic number (from the periodic table)
gives protons, the mass number is the sum of protons and neutrons, and neutral atoms have equal
protons and electrons. Option A uses the atomic number for neutrons, which is a common error.
Correct Answer: B
Q6. Which element is classified as a metalloid?
A. Sodium (Na)
B. Silicon (Si)
C. Chlorine (Cl)
D. Iron (Fe)
Rationale: The best answer is B. Silicon sits along the staircase line on the periodic table and exhibits
properties intermediate between metals and nonmetals—it's a semiconductor, it has a metallic luster
but is brittle, and it forms covalent network solids. Sodium is a Group 1 alkali metal, chlorine is a halogen
(nonmetal), and iron is a transition metal. The metalloids are B, Si, Ge, As, Sb, Te, and sometimes Po, all
located along the diagonal boundary between metals and nonmetals.
Correct Answer: B
Q7. Which of the following elements is an alkaline earth metal?
, A. Potassium (K)
B. Magnesium (Mg)
C. Aluminum (Al)
D. Argon (Ar)
Rationale: The best answer is B. Magnesium is in Group 2 of the periodic table, which is the alkaline
earth metal group. These elements have two valence electrons and form +2 cations. Potassium is an
alkali metal (Group 1), aluminum is a post-transition metal (Group 13), and argon is a noble gas (Group
18). The group number tells you a lot about an element's properties, so learning the group names pays
off on exams.
Correct Answer: B
Q8. Calculate the average atomic mass of element X given the following isotope data:
Table
Isotope Mass (amu) Natural Abundance
X-10 10.012 19.9%
X-11 11.009 80.1%
A. 10.50 amu
B. 10.81 amu
C. 11.00 amu
D. 21.02 amu
Rationale: The best answer is B. Average atomic mass is a weighted average: (10.012 × 0.199) + (11.009
× 0.801) = 1.992 + 8.818 = 10.81 amu. You multiply each isotope's mass by its fractional abundance and
add the results. A common mistake is simply averaging the two masses without weighting by
abundance, which gives about 10.51, or adding the masses together. This element is boron, by the way,
with an actual average atomic mass of about 10.81 amu.
Correct Answer: B
Q9. How many electrons are in the third energy level (n = 3) of a neutral phosphorus atom?
