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MISTRY OPENSTAX 2E EXAM WITH VERIFIED ANSWERS
DETAILED RATIONALES GRADED A+
MISTRY OpenStax 2e — COMPLETE TEST BANK (2026 UPDATED)
SECTION 1: ESSENTIAL IDEAS & MEASUREMENT (Questions 1–25)
1. The atomic number of an element equals the number of:
A. neutrons
B. protons
C. electrons
D. nucleons
Rationale: The atomic number is defined as the number of protons in the nucleus of an atom.
This uniquely identifies each element. While neutral atoms have equal numbers of protons and
electrons, the atomic number specifically refers to protons. Nucleons refer to both protons and
neutrons combined (mass number).
2. Which of the following is an example of a physical property?
A. Flammability
B. Reactivity with acid
C. Density
D. Toxicity
Rationale: Density is a physical property because it can be observed without changing the
chemical identity of the substance. Flammability, reactivity with acid, and toxicity are chemical
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properties that describe how a substance interacts with other substances to form new
substances.
3. How many significant figures are in the measurement 0.004560?
A. 3
B. 4
C. 5
D. 7
Rationale: The leading zeros (0.00) are not significant. The digits 4, 5, 6 are significant, and the
trailing zero after 6 is significant because it comes after a decimal point and a non-zero digit.
Therefore, there are 4 significant figures.
4. Which of the following represents a chemical change?
A. Melting ice
B. Dissolving sugar in water
C. Rusting of iron
D. Boiling water
Rationale: Rusting of iron is a chemical change because it produces a new substance (iron
oxide) with different chemical properties. Melting, dissolving, and boiling are physical changes
that do not alter chemical identity.
5. What is the SI unit for the amount of a substance?
A. Gram
B. Liter
C. Mole
D. Kelvin
Rationale: The mole (mol) is the SI unit for amount of substance. The gram measures mass, the
liter measures volume, and the kelvin measures temperature.
6. Which of the following is a homogeneous mixture?
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A. Sand and water
B. Salt water
C. Oil and water
D. Granite rock
Rationale: Salt water is a homogeneous mixture (solution) because the salt is uniformly
distributed throughout the water and has a single visible phase. Sand and water, oil and water,
and granite are heterogeneous mixtures.
7. Convert 25.0 °C to Kelvin.
A. 248.15 K
B. 298.15 K
C. 273.15 K
D. 323.15 K
Rationale: To convert from Celsius to Kelvin, add 273.15: 25.0 + 273.15 = 298.15 K.
8. Which of the following is a noble gas?
A. Oxygen
B. Nitrogen
C. Argon
D. Chlorine
Rationale: Argon (Ar) is a noble gas in Group 18 of the periodic table. Oxygen, nitrogen, and
chlorine are not noble gases.
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9. How many protons, neutrons, and electrons are in an atom of Fe?
A. 26 protons, 30 neutrons, 26 electrons
B. 26 protons, 26 neutrons, 30 electrons
C. 30 protons, 26 neutrons, 26 electrons
D. 56 protons, 26 neutrons, 56 electrons
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Rationale: Iron (Fe) has an atomic number of 26, meaning it has 26 protons and 26 electrons.
The mass number is 56, so the number of neutrons is 56 − 26 = 30.
10. Which of the following is an intensive property?
A. Mass
B. Volume
C. Temperature
D. Length
Rationale: Intensive properties do not depend on the amount of substance present.
Temperature is intensive, while mass, volume, and length are extensive properties that depend
on the amount of substance.
11. What is the correct scientific notation for 0.00045?
A. 4.5 × 10−4
B. 4.5 × 104
C. 45 × 10−5
D. 0.45 × 10−3
Rationale: 0.00045 = 4.5 × 10⁻⁴. The decimal point is moved four places to the right to obtain a
number between 1 and 10.
12. Which of the following is a diatomic element?
A. Helium
B. Hydrogen
C. Carbon
D. Sodium
Rationale: Hydrogen (H₂) is a diatomic element, meaning it naturally exists as two atoms
bonded together. Helium, carbon, and sodium do not exist as diatomic molecules under normal
conditions.
13. What is the density of a substance with a mass of 25.0 g and a volume of 5.0 mL?
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MISTRY OPENSTAX 2E EXAM WITH VERIFIED ANSWERS
DETAILED RATIONALES GRADED A+
MISTRY OpenStax 2e — COMPLETE TEST BANK (2026 UPDATED)
SECTION 1: ESSENTIAL IDEAS & MEASUREMENT (Questions 1–25)
1. The atomic number of an element equals the number of:
A. neutrons
B. protons
C. electrons
D. nucleons
Rationale: The atomic number is defined as the number of protons in the nucleus of an atom.
This uniquely identifies each element. While neutral atoms have equal numbers of protons and
electrons, the atomic number specifically refers to protons. Nucleons refer to both protons and
neutrons combined (mass number).
2. Which of the following is an example of a physical property?
A. Flammability
B. Reactivity with acid
C. Density
D. Toxicity
Rationale: Density is a physical property because it can be observed without changing the
chemical identity of the substance. Flammability, reactivity with acid, and toxicity are chemical
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properties that describe how a substance interacts with other substances to form new
substances.
3. How many significant figures are in the measurement 0.004560?
A. 3
B. 4
C. 5
D. 7
Rationale: The leading zeros (0.00) are not significant. The digits 4, 5, 6 are significant, and the
trailing zero after 6 is significant because it comes after a decimal point and a non-zero digit.
Therefore, there are 4 significant figures.
4. Which of the following represents a chemical change?
A. Melting ice
B. Dissolving sugar in water
C. Rusting of iron
D. Boiling water
Rationale: Rusting of iron is a chemical change because it produces a new substance (iron
oxide) with different chemical properties. Melting, dissolving, and boiling are physical changes
that do not alter chemical identity.
5. What is the SI unit for the amount of a substance?
A. Gram
B. Liter
C. Mole
D. Kelvin
Rationale: The mole (mol) is the SI unit for amount of substance. The gram measures mass, the
liter measures volume, and the kelvin measures temperature.
6. Which of the following is a homogeneous mixture?
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A. Sand and water
B. Salt water
C. Oil and water
D. Granite rock
Rationale: Salt water is a homogeneous mixture (solution) because the salt is uniformly
distributed throughout the water and has a single visible phase. Sand and water, oil and water,
and granite are heterogeneous mixtures.
7. Convert 25.0 °C to Kelvin.
A. 248.15 K
B. 298.15 K
C. 273.15 K
D. 323.15 K
Rationale: To convert from Celsius to Kelvin, add 273.15: 25.0 + 273.15 = 298.15 K.
8. Which of the following is a noble gas?
A. Oxygen
B. Nitrogen
C. Argon
D. Chlorine
Rationale: Argon (Ar) is a noble gas in Group 18 of the periodic table. Oxygen, nitrogen, and
chlorine are not noble gases.
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9. How many protons, neutrons, and electrons are in an atom of Fe?
A. 26 protons, 30 neutrons, 26 electrons
B. 26 protons, 26 neutrons, 30 electrons
C. 30 protons, 26 neutrons, 26 electrons
D. 56 protons, 26 neutrons, 56 electrons
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Rationale: Iron (Fe) has an atomic number of 26, meaning it has 26 protons and 26 electrons.
The mass number is 56, so the number of neutrons is 56 − 26 = 30.
10. Which of the following is an intensive property?
A. Mass
B. Volume
C. Temperature
D. Length
Rationale: Intensive properties do not depend on the amount of substance present.
Temperature is intensive, while mass, volume, and length are extensive properties that depend
on the amount of substance.
11. What is the correct scientific notation for 0.00045?
A. 4.5 × 10−4
B. 4.5 × 104
C. 45 × 10−5
D. 0.45 × 10−3
Rationale: 0.00045 = 4.5 × 10⁻⁴. The decimal point is moved four places to the right to obtain a
number between 1 and 10.
12. Which of the following is a diatomic element?
A. Helium
B. Hydrogen
C. Carbon
D. Sodium
Rationale: Hydrogen (H₂) is a diatomic element, meaning it naturally exists as two atoms
bonded together. Helium, carbon, and sodium do not exist as diatomic molecules under normal
conditions.
13. What is the density of a substance with a mass of 25.0 g and a volume of 5.0 mL?
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