MSU CEM 141 Final Exam Newest Actual Exam With Complete Questions And
Correct Detailed Answers (Verified Answers) |Already Graded A+
Question 1
Which of the following represents a chemical property of hydrogen gas?
A) It is less dense than air.
B) It is colorless and odorless.
C) It reacts explosively with oxygen to form water.
D) It can be liquefied at very low temperatures.
E) It has a boiling point of 20.28 K.
Correct Answer: C) It reacts explosively with oxygen to form water.
Rationale: A chemical property describes the ability of a substance to undergo a specific
chemical change that alters its identity. Reactivity with oxygen is a chemical property
because it results in the formation of a new substance (water). Options A, B, D, and E are
physical properties because they describe the substance's state or behavior without
changing its molecular composition.
Question 2
How many significant figures are in the measurement 0.005080 grams?
A) 3
B) 4
C) 5
D) 6
E) 7
Correct Answer: B) 4
Rationale: In significant figure rules: 1) Leading zeros (0.00...) are never significant. 2) Non-
zero digits (5, 8) are always significant. 3) Captive zeros (between non-zero digits, like the 0
in 508) are significant. 4) Trailing zeros in a decimal number (the final 0) are significant.
Therefore, only "5080" are significant.
Question 3
Which of the following is an intensive property?
A) Mass
B) Volume
C) Density
D) Total heat content
E) Length
Correct Answer: C) Density
Rationale: An intensive property is independent of the amount of substance present.
Whether you have a drop of water or a gallon, the density remains 1.0 g/mL. Extensive
, 2
properties, such as mass, volume, and length, change based on the amount of matter being
measured.
Question 4
If an object has a mass of 45.0 g and a volume of 15.0 cm³, what is its density expressed with the
correct number of significant figures?
A) 3 g/cm³
B) 3.0 g/cm³
C) 3.00 g/cm³
D) 0.333 g/cm³
E) 3.000 g/cm³
Correct Answer: C) 3.00 g/cm³
Rationale: Density = Mass / Volume. 45..0 = 3. Both 45.0 and 15.0 have three
significant figures. In multiplication and division, the result must have the same number of
significant figures as the measurement with the fewest significant figures. Thus, the answer
must be reported as 3.00.
Question 5
Which of the following is a pure substance that cannot be broken down by chemical means?
A) Water
B) Methane
C) Nitrogen
D) Sodium Chloride
E) Air
Correct Answer: C) Nitrogen
Rationale: Pure substances are either elements or compounds. Nitrogen (N₂) is an element,
which is the simplest form of matter that has a unique set of properties and cannot be
broken down chemically. Water, Methane, and Sodium Chloride are compounds that can
be broken down into elements. Air is a mixture.
Question 6
An atom of the isotope Sulfur-34 (atomic number 16) contains:
A) 16 protons, 16 electrons, 16 neutrons
B) 16 protons, 16 electrons, 18 neutrons
C) 18 protons, 18 electrons, 16 neutrons
D) 34 protons, 34 electrons, 16 neutrons
E) 16 protons, 18 electrons, 18 neutrons
Correct Answer: B) 16 protons, 16 electrons, 18 neutrons
Rationale: The atomic number (16) identifies the number of protons. In a neutral atom,
, 3
protons equal electrons. The mass number (34) is the sum of protons and neutrons.
Therefore, Neutrons = Mass Number - Protons = 34 - 16 = 18.
Question 7
The gold foil experiment performed by Rutherford’s team led to which conclusion?
A) Electrons are embedded in a uniform sphere of positive charge.
B) Most of the atom is empty space with a tiny, dense, positive nucleus.
C) Electrons travel in fixed circular orbits around the nucleus.
D) Atoms are indivisible hard spheres.
E) Neutrons exist within the nucleus to provide stability.
Correct Answer: B) Most of the atom is empty space with a tiny, dense, positive nucleus.
Rationale: Because most alpha particles passed through the gold foil, Rutherford concluded
the atom is mostly empty space. The rare deflection of particles at large angles indicated
that the positive charge and most of the mass are concentrated in a very small central
region called the nucleus.
Question 8
Which of the following pairs represent isotopes?
A) O₂ and O₃
B) ¹²C and ¹⁴C
C) Na and Na⁺
D) H₂O and H₂O₂
E) Diamond and Graphite
Correct Answer: B) ¹²C and ¹⁴C
Rationale: Isotopes are atoms of the same element (same number of protons) that have
different numbers of neutrons (different mass numbers). ¹²C and ¹⁴C both have 6 protons
but differ in neutrons. O₂ and O₃ are allotropes; Na and Na⁺ are an atom and an ion; H₂O
and H₂O₂ are different compounds.
Question 9
What is the average atomic mass of an element with two isotopes: Isotope A (20.0 amu, 90.0%
abundance) and Isotope B (22.0 amu, 10.0% abundance)?
A) 21.0 amu
B) 20.2 amu
C) 20.0 amu
D) 21.8 amu
E) 22.0 amu
, 4
Correct Answer: B) 20.2 amu
Rationale: Average atomic mass = (Mass A × Fraction A) + (Mass B × Fraction B).
Average mass = (20.0 × 0.90) + (22.0 × 0.10) = 18.0 + 2.2 = 20.2 amu.
Question 10
Which group on the periodic table is characterized by having a full valence shell and being
generally unreactive?
A) Alkali Metals
B) Alkaline Earth Metals
C) Halogens
D) Noble Gases
E) Chalcogens
Correct Answer: D) Noble Gases
Rationale: Noble gases (Group 18) have a complete octet of valence electrons (except
Helium, which has 2), making them exceptionally stable and chemically inert under
standard conditions.
Question 11
Which of the following elements is a metalloid?
A) Carbon
B) Silicon
C) Aluminum
D) Phosphorus
E) Iron
Correct Answer: B) Silicon
Rationale: Metalloids are elements that have properties intermediate between metals and
nonmetals. Silicon (Si) is found along the "staircase" line on the periodic table and is a
classic metalloid. Aluminum is a post-transition metal.
Question 12
Which element has the electron configuration [Ar] 4s² 3d¹⁰ 4p³?
A) Phosphorus
B) Arsenic
C) Selenium
D) Antimony
E) Germanium
Correct Answer: B) Arsenic
Rationale: Argon (Ar) represents 18 electrons. Adding 4s² (2), 3d¹⁰ (10), and 4p³ (3) gives a
total of 18 + 2 + 10 + 3 = 33 electrons. The element with atomic number 33 is Arsenic (As).
Correct Detailed Answers (Verified Answers) |Already Graded A+
Question 1
Which of the following represents a chemical property of hydrogen gas?
A) It is less dense than air.
B) It is colorless and odorless.
C) It reacts explosively with oxygen to form water.
D) It can be liquefied at very low temperatures.
E) It has a boiling point of 20.28 K.
Correct Answer: C) It reacts explosively with oxygen to form water.
Rationale: A chemical property describes the ability of a substance to undergo a specific
chemical change that alters its identity. Reactivity with oxygen is a chemical property
because it results in the formation of a new substance (water). Options A, B, D, and E are
physical properties because they describe the substance's state or behavior without
changing its molecular composition.
Question 2
How many significant figures are in the measurement 0.005080 grams?
A) 3
B) 4
C) 5
D) 6
E) 7
Correct Answer: B) 4
Rationale: In significant figure rules: 1) Leading zeros (0.00...) are never significant. 2) Non-
zero digits (5, 8) are always significant. 3) Captive zeros (between non-zero digits, like the 0
in 508) are significant. 4) Trailing zeros in a decimal number (the final 0) are significant.
Therefore, only "5080" are significant.
Question 3
Which of the following is an intensive property?
A) Mass
B) Volume
C) Density
D) Total heat content
E) Length
Correct Answer: C) Density
Rationale: An intensive property is independent of the amount of substance present.
Whether you have a drop of water or a gallon, the density remains 1.0 g/mL. Extensive
, 2
properties, such as mass, volume, and length, change based on the amount of matter being
measured.
Question 4
If an object has a mass of 45.0 g and a volume of 15.0 cm³, what is its density expressed with the
correct number of significant figures?
A) 3 g/cm³
B) 3.0 g/cm³
C) 3.00 g/cm³
D) 0.333 g/cm³
E) 3.000 g/cm³
Correct Answer: C) 3.00 g/cm³
Rationale: Density = Mass / Volume. 45..0 = 3. Both 45.0 and 15.0 have three
significant figures. In multiplication and division, the result must have the same number of
significant figures as the measurement with the fewest significant figures. Thus, the answer
must be reported as 3.00.
Question 5
Which of the following is a pure substance that cannot be broken down by chemical means?
A) Water
B) Methane
C) Nitrogen
D) Sodium Chloride
E) Air
Correct Answer: C) Nitrogen
Rationale: Pure substances are either elements or compounds. Nitrogen (N₂) is an element,
which is the simplest form of matter that has a unique set of properties and cannot be
broken down chemically. Water, Methane, and Sodium Chloride are compounds that can
be broken down into elements. Air is a mixture.
Question 6
An atom of the isotope Sulfur-34 (atomic number 16) contains:
A) 16 protons, 16 electrons, 16 neutrons
B) 16 protons, 16 electrons, 18 neutrons
C) 18 protons, 18 electrons, 16 neutrons
D) 34 protons, 34 electrons, 16 neutrons
E) 16 protons, 18 electrons, 18 neutrons
Correct Answer: B) 16 protons, 16 electrons, 18 neutrons
Rationale: The atomic number (16) identifies the number of protons. In a neutral atom,
, 3
protons equal electrons. The mass number (34) is the sum of protons and neutrons.
Therefore, Neutrons = Mass Number - Protons = 34 - 16 = 18.
Question 7
The gold foil experiment performed by Rutherford’s team led to which conclusion?
A) Electrons are embedded in a uniform sphere of positive charge.
B) Most of the atom is empty space with a tiny, dense, positive nucleus.
C) Electrons travel in fixed circular orbits around the nucleus.
D) Atoms are indivisible hard spheres.
E) Neutrons exist within the nucleus to provide stability.
Correct Answer: B) Most of the atom is empty space with a tiny, dense, positive nucleus.
Rationale: Because most alpha particles passed through the gold foil, Rutherford concluded
the atom is mostly empty space. The rare deflection of particles at large angles indicated
that the positive charge and most of the mass are concentrated in a very small central
region called the nucleus.
Question 8
Which of the following pairs represent isotopes?
A) O₂ and O₃
B) ¹²C and ¹⁴C
C) Na and Na⁺
D) H₂O and H₂O₂
E) Diamond and Graphite
Correct Answer: B) ¹²C and ¹⁴C
Rationale: Isotopes are atoms of the same element (same number of protons) that have
different numbers of neutrons (different mass numbers). ¹²C and ¹⁴C both have 6 protons
but differ in neutrons. O₂ and O₃ are allotropes; Na and Na⁺ are an atom and an ion; H₂O
and H₂O₂ are different compounds.
Question 9
What is the average atomic mass of an element with two isotopes: Isotope A (20.0 amu, 90.0%
abundance) and Isotope B (22.0 amu, 10.0% abundance)?
A) 21.0 amu
B) 20.2 amu
C) 20.0 amu
D) 21.8 amu
E) 22.0 amu
, 4
Correct Answer: B) 20.2 amu
Rationale: Average atomic mass = (Mass A × Fraction A) + (Mass B × Fraction B).
Average mass = (20.0 × 0.90) + (22.0 × 0.10) = 18.0 + 2.2 = 20.2 amu.
Question 10
Which group on the periodic table is characterized by having a full valence shell and being
generally unreactive?
A) Alkali Metals
B) Alkaline Earth Metals
C) Halogens
D) Noble Gases
E) Chalcogens
Correct Answer: D) Noble Gases
Rationale: Noble gases (Group 18) have a complete octet of valence electrons (except
Helium, which has 2), making them exceptionally stable and chemically inert under
standard conditions.
Question 11
Which of the following elements is a metalloid?
A) Carbon
B) Silicon
C) Aluminum
D) Phosphorus
E) Iron
Correct Answer: B) Silicon
Rationale: Metalloids are elements that have properties intermediate between metals and
nonmetals. Silicon (Si) is found along the "staircase" line on the periodic table and is a
classic metalloid. Aluminum is a post-transition metal.
Question 12
Which element has the electron configuration [Ar] 4s² 3d¹⁰ 4p³?
A) Phosphorus
B) Arsenic
C) Selenium
D) Antimony
E) Germanium
Correct Answer: B) Arsenic
Rationale: Argon (Ar) represents 18 electrons. Adding 4s² (2), 3d¹⁰ (10), and 4p³ (3) gives a
total of 18 + 2 + 10 + 3 = 33 electrons. The element with atomic number 33 is Arsenic (As).
