PORTAGE LEARNING CHEM 103 EXAM
MASTERY MODULES 1 to 6 AND FINAL
150 DETAILED CORRECT ANSWERS
WITH RATIONALES VERIFIED
SOLUTIONS GRADE A+ SYLLABUS
COMPANION | INSTANT DOWNLOAD
Chem 103 Module 1 to 6 Exam
Question 1
A student is performing a laboratory experiment and measures the mass
of a solid sample to be 0.045020 grams. How many significant figures
are present in this recorded measurement?
A. Three significant figures
B. Four significant figures
C. Five significant figures
D. Six significant figures
Correct Answer: C. Five significant figures
Rationale: In significant figure rules, leading zeros (zeros before the
first non-zero digit) are never significant, so the zeros in "0.04" do not
count. Captive zeros (zeros between non-zero numbers) are always
significant, meaning the "0" between 5 and 2 counts. Trailing zeros to
the right of a decimal point are also significant, meaning the final "0"
counts. Therefore, the significant digits are 4, 5, 0, 2, and 0, giving a
total of five.
Question 2
An unknown liquid sample has a measured mass of 38.42 grams and
occupies a volume of 42.60 milliliters. What is the density of this liquid
reported to the correct number of significant figures?
A. 0.90 g/mL
B. 0.9019 g/mL
,C. 0.90188 g/mL
D. 1.109 g/mL
Correct Answer: B. 0.9019 g/mL
Rationale: Density is calculated by dividing mass by volume (D = m/V).
Using the values given: 38.42 g / 42.60 mL = 0.9018779... g/mL. When
multiplying or dividing, the final answer must match the fewest
number of significant figures from the starting values. Both 38.42 and
42.60 have four significant figures. Rounding the result to four
significant figures yields 0.9019 g/mL.
Question 3
Which of the following statements correctly identifies a physical change?
A. A piece of magnesium ribbon burns in air with a bright white flame to
form a white powder.
B. Solid iodine crystals undergo sublimation when heated to form a
vibrant purple vapor.
C. A sample of iron metal rusts over time when exposed to moist
atmospheric oxygen.
D. Zinc metal dissolves in a hydrochloric acid solution, producing
bubbles of hydrogen gas.
Correct Answer: B. Solid iodine crystals undergo sublimation
when heated to form a vibrant purple vapor.
Rationale: A physical change alters the physical state or appearance of
a substance without transforming its chemical composition.
Sublimation is a phase change from a solid directly to a gas (I₂(s) →
I₂(g)), meaning the chemical identity of iodine remains unchanged.
Burning magnesium, rusting iron, and zinc reacting with acid are all
chemical changes because new chemical substances with distinct
properties are created.
Question 4
According to early atomic theory and the modern nuclear model of the
atom, which of the following statements regarding subatomic particles is
true?
A. Protons and electrons are located inside the dense nucleus, while
neutrons orbit around it.
B. The mass of an electron is roughly equal to the mass of a proton.
C. The atomic number of an element is defined as the total sum of its
protons and neutrons.
,D. Protons and neutrons reside inside the nucleus, which holds nearly all
of the atom's mass. [1]
Correct Answer: D. Protons and neutrons reside inside the
nucleus, which holds nearly all of the atom's mass.
Rationale: The modern nuclear model of the atom establishes that the
small, dense central nucleus contains protons and neutrons, which
account for virtually all of the atom's mass. Electrons possess negligible
mass and occupy the large cloud space surrounding the nucleus. The
atomic number equals the number of protons alone, whereas the mass
number represents the sum of protons and neutrons.
Question 5
An isotope of a specific neutral atom contains 26 protons, 30 neutrons,
and 26 electrons. Which of the following symbols correctly identifies this
isotope?
A. ⁵⁶₃₀Zn
B. ³⁰₂₆Fe
C. ⁵⁶₂₆Fe
D. ⁵⁶₂₆Ba
Correct Answer: C. ⁵⁶₂₆Fe
Rationale: The atomic number (Z), which is the number of protons,
identifies the element. An atomic number of 26 corresponds to iron (Fe),
which goes on the bottom left of the nuclear symbol. The mass number
(A) represents the sum of protons and neutrons (26 + 30 = 56), which
goes on the top left of the symbol. Therefore, the correct nuclear symbol
is ⁵⁶₂₆Fe.
Question 6
What is the correct chemical name for the ionic compound represented
by the formula Fe₂(SO₄)₃?
A. Iron(II) trisulfate
B. Iron(III) sulfate
C. Diiron trisulfate
Δ. Iron persulfate
Correct Answer: B. Iron(III) sulfate
Rationale: Fe₂(SO₄)₃ is an ionic compound made of iron cations and
polyatomic sulfate anions (SO₄²⁻). Since sulfate has a -2 charge and
there are three of them, the total negative charge is -6. To balance this,
the two iron ions must share a +6 charge, meaning each iron ion
, carries a +3 charge (Fe³⁺). Iron is a transition metal that requires
Roman numerals to indicate its charge, yielding iron(III) sulfate. Greek
prefixes are only used for covalent compounds.
Question 7
Which of the following choices represents the correct empirical formula
and chemical name for a molecular compound formed between carbon
and oxygen containing two oxygen atoms?
Α. CO₂, Carbon dioxide
B. C₂O, Dicarbon monoxide
C. CO₂, Carbon(IV) oxide
D. CO, Carbon monoxide [1]
Correct Answer: A. CO₂, Carbon dioxide
Rationale: A molecular (covalent) compound consisting of one carbon
atom and two oxygen atoms is represented by the formula CO₂.
Covalent nomenclature requires Greek prefixes to define atom counts,
making its name carbon dioxide. Because it cannot be simplified into a
smaller whole-number ratio, CO₂ is also its empirical formula.
Question 8
What is the molecular mass of the compound aluminum carbonate,
Al₂(CO₃)₃, calculated using the following atomic masses: Al = 26.98
amu, C = 12.01 amu, O = 16.00 amu?
A. 86.99 amu
B. 113.99 amu
C. 233.99 amu
D. 242.01 amu
Correct Answer: C. 233.99 amu
Rationale: To calculate the molecular mass, multiply the atomic mass
of each element by its total number of atoms in the formula:
Al: 2 × 26.98 = 53.96 amu
C: 3 × 12.01 = 36.03 amu
O: 9 × 16.00 = 144.00 amu
Summing these values: 53.96 + 36.03 + 144.00 = 233.99 amu.
Question 9
How many moles of substance are contained within a 45.20-gram
sample of pure sodium chloride (NaCl, molar mass = 58.44 g/mol)?
A. 0.7734 moles
MASTERY MODULES 1 to 6 AND FINAL
150 DETAILED CORRECT ANSWERS
WITH RATIONALES VERIFIED
SOLUTIONS GRADE A+ SYLLABUS
COMPANION | INSTANT DOWNLOAD
Chem 103 Module 1 to 6 Exam
Question 1
A student is performing a laboratory experiment and measures the mass
of a solid sample to be 0.045020 grams. How many significant figures
are present in this recorded measurement?
A. Three significant figures
B. Four significant figures
C. Five significant figures
D. Six significant figures
Correct Answer: C. Five significant figures
Rationale: In significant figure rules, leading zeros (zeros before the
first non-zero digit) are never significant, so the zeros in "0.04" do not
count. Captive zeros (zeros between non-zero numbers) are always
significant, meaning the "0" between 5 and 2 counts. Trailing zeros to
the right of a decimal point are also significant, meaning the final "0"
counts. Therefore, the significant digits are 4, 5, 0, 2, and 0, giving a
total of five.
Question 2
An unknown liquid sample has a measured mass of 38.42 grams and
occupies a volume of 42.60 milliliters. What is the density of this liquid
reported to the correct number of significant figures?
A. 0.90 g/mL
B. 0.9019 g/mL
,C. 0.90188 g/mL
D. 1.109 g/mL
Correct Answer: B. 0.9019 g/mL
Rationale: Density is calculated by dividing mass by volume (D = m/V).
Using the values given: 38.42 g / 42.60 mL = 0.9018779... g/mL. When
multiplying or dividing, the final answer must match the fewest
number of significant figures from the starting values. Both 38.42 and
42.60 have four significant figures. Rounding the result to four
significant figures yields 0.9019 g/mL.
Question 3
Which of the following statements correctly identifies a physical change?
A. A piece of magnesium ribbon burns in air with a bright white flame to
form a white powder.
B. Solid iodine crystals undergo sublimation when heated to form a
vibrant purple vapor.
C. A sample of iron metal rusts over time when exposed to moist
atmospheric oxygen.
D. Zinc metal dissolves in a hydrochloric acid solution, producing
bubbles of hydrogen gas.
Correct Answer: B. Solid iodine crystals undergo sublimation
when heated to form a vibrant purple vapor.
Rationale: A physical change alters the physical state or appearance of
a substance without transforming its chemical composition.
Sublimation is a phase change from a solid directly to a gas (I₂(s) →
I₂(g)), meaning the chemical identity of iodine remains unchanged.
Burning magnesium, rusting iron, and zinc reacting with acid are all
chemical changes because new chemical substances with distinct
properties are created.
Question 4
According to early atomic theory and the modern nuclear model of the
atom, which of the following statements regarding subatomic particles is
true?
A. Protons and electrons are located inside the dense nucleus, while
neutrons orbit around it.
B. The mass of an electron is roughly equal to the mass of a proton.
C. The atomic number of an element is defined as the total sum of its
protons and neutrons.
,D. Protons and neutrons reside inside the nucleus, which holds nearly all
of the atom's mass. [1]
Correct Answer: D. Protons and neutrons reside inside the
nucleus, which holds nearly all of the atom's mass.
Rationale: The modern nuclear model of the atom establishes that the
small, dense central nucleus contains protons and neutrons, which
account for virtually all of the atom's mass. Electrons possess negligible
mass and occupy the large cloud space surrounding the nucleus. The
atomic number equals the number of protons alone, whereas the mass
number represents the sum of protons and neutrons.
Question 5
An isotope of a specific neutral atom contains 26 protons, 30 neutrons,
and 26 electrons. Which of the following symbols correctly identifies this
isotope?
A. ⁵⁶₃₀Zn
B. ³⁰₂₆Fe
C. ⁵⁶₂₆Fe
D. ⁵⁶₂₆Ba
Correct Answer: C. ⁵⁶₂₆Fe
Rationale: The atomic number (Z), which is the number of protons,
identifies the element. An atomic number of 26 corresponds to iron (Fe),
which goes on the bottom left of the nuclear symbol. The mass number
(A) represents the sum of protons and neutrons (26 + 30 = 56), which
goes on the top left of the symbol. Therefore, the correct nuclear symbol
is ⁵⁶₂₆Fe.
Question 6
What is the correct chemical name for the ionic compound represented
by the formula Fe₂(SO₄)₃?
A. Iron(II) trisulfate
B. Iron(III) sulfate
C. Diiron trisulfate
Δ. Iron persulfate
Correct Answer: B. Iron(III) sulfate
Rationale: Fe₂(SO₄)₃ is an ionic compound made of iron cations and
polyatomic sulfate anions (SO₄²⁻). Since sulfate has a -2 charge and
there are three of them, the total negative charge is -6. To balance this,
the two iron ions must share a +6 charge, meaning each iron ion
, carries a +3 charge (Fe³⁺). Iron is a transition metal that requires
Roman numerals to indicate its charge, yielding iron(III) sulfate. Greek
prefixes are only used for covalent compounds.
Question 7
Which of the following choices represents the correct empirical formula
and chemical name for a molecular compound formed between carbon
and oxygen containing two oxygen atoms?
Α. CO₂, Carbon dioxide
B. C₂O, Dicarbon monoxide
C. CO₂, Carbon(IV) oxide
D. CO, Carbon monoxide [1]
Correct Answer: A. CO₂, Carbon dioxide
Rationale: A molecular (covalent) compound consisting of one carbon
atom and two oxygen atoms is represented by the formula CO₂.
Covalent nomenclature requires Greek prefixes to define atom counts,
making its name carbon dioxide. Because it cannot be simplified into a
smaller whole-number ratio, CO₂ is also its empirical formula.
Question 8
What is the molecular mass of the compound aluminum carbonate,
Al₂(CO₃)₃, calculated using the following atomic masses: Al = 26.98
amu, C = 12.01 amu, O = 16.00 amu?
A. 86.99 amu
B. 113.99 amu
C. 233.99 amu
D. 242.01 amu
Correct Answer: C. 233.99 amu
Rationale: To calculate the molecular mass, multiply the atomic mass
of each element by its total number of atoms in the formula:
Al: 2 × 26.98 = 53.96 amu
C: 3 × 12.01 = 36.03 amu
O: 9 × 16.00 = 144.00 amu
Summing these values: 53.96 + 36.03 + 144.00 = 233.99 amu.
Question 9
How many moles of substance are contained within a 45.20-gram
sample of pure sodium chloride (NaCl, molar mass = 58.44 g/mol)?
A. 0.7734 moles
