HESI A2 Chemistry Practice
Examination 100 Questions And
Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A Instant
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1. Which subatomic particle has a negative electrical charge?
A) Proton
B) Neutron
C) Electron
D) Positron
Rationale: Electrons carry a negative charge and are located in the electron
cloud surrounding the nucleus. Protons are positively charged, and neutrons
are neutral.
2. What is the atomic number of an element?
A) The number of neutrons
B) The number of protons and neutrons
C) The total number of electrons and neutrons
D) The number of protons
Rationale: The atomic number uniquely identifies an element and equals the
number of protons in its nucleus. In a neutral atom, the number of electrons
also equals the atomic number, but the defining characteristic is the proton
count.
,3. An atom contains 11 protons, 12 neutrons, and 11 electrons. What is its
mass number?
A) 11
B) 12
C) 23
D) 34
Rationale: Mass number is calculated by adding protons and neutrons: 11 +
12 = 23. Electrons have negligible mass and are not included in the mass
number calculation.
4. Which element has the chemical symbol Na?
A) Nitrogen
B) Neon
C) Sodium
D) Nickel
Rationale: Na is the chemical symbol for sodium, derived from the Latin name
natrium. Nitrogen is N, neon is Ne, and nickel is Ni.
5. Which of the following is a characteristic of an ionic bond?
A) Electrons are always shared equally
B) Electrons are transferred between atoms
C) Only nonmetals participate
D) It occurs only between identical atoms
Rationale: Ionic bonding involves the transfer of electrons from a metal to a
nonmetal, creating oppositely charged ions that attract one another.
Covalent bonds involve electron sharing.
6. Which type of bond involves the sharing of electrons between atoms?
A) Ionic
B) Metallic
, C) Covalent
D) Hydrogen
Rationale: Covalent bonds form when atoms share electrons, commonly
between nonmetal atoms. Ionic bonding involves electron transfer rather
than sharing.
7. What is the chemical formula for water?
A) CO₂
B) O₂
C) H₂
D) H₂O
Rationale: A water molecule contains two hydrogen atoms covalently bonded
to one oxygen atom, giving it the formula H₂O.
8. Which substance is considered an acid?
A) NaOH
B) KOH
C) HCl
D) NaCl
Rationale: Hydrochloric acid (HCl) is a strong acid that dissociates extensively
in aqueous solution to produce hydrogen ions. NaOH and KOH are bases.
9. What is the pH of a neutral aqueous solution at 25°C?
A) 0
B) 7
C) 10
D) 14
Rationale: At 25°C, a neutral solution has equal concentrations of H⁺ and OH⁻
ions (1.0 × 10⁻⁷ M), resulting in a pH of exactly 7.
Examination 100 Questions And
Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A Instant
Download Pdf
1. Which subatomic particle has a negative electrical charge?
A) Proton
B) Neutron
C) Electron
D) Positron
Rationale: Electrons carry a negative charge and are located in the electron
cloud surrounding the nucleus. Protons are positively charged, and neutrons
are neutral.
2. What is the atomic number of an element?
A) The number of neutrons
B) The number of protons and neutrons
C) The total number of electrons and neutrons
D) The number of protons
Rationale: The atomic number uniquely identifies an element and equals the
number of protons in its nucleus. In a neutral atom, the number of electrons
also equals the atomic number, but the defining characteristic is the proton
count.
,3. An atom contains 11 protons, 12 neutrons, and 11 electrons. What is its
mass number?
A) 11
B) 12
C) 23
D) 34
Rationale: Mass number is calculated by adding protons and neutrons: 11 +
12 = 23. Electrons have negligible mass and are not included in the mass
number calculation.
4. Which element has the chemical symbol Na?
A) Nitrogen
B) Neon
C) Sodium
D) Nickel
Rationale: Na is the chemical symbol for sodium, derived from the Latin name
natrium. Nitrogen is N, neon is Ne, and nickel is Ni.
5. Which of the following is a characteristic of an ionic bond?
A) Electrons are always shared equally
B) Electrons are transferred between atoms
C) Only nonmetals participate
D) It occurs only between identical atoms
Rationale: Ionic bonding involves the transfer of electrons from a metal to a
nonmetal, creating oppositely charged ions that attract one another.
Covalent bonds involve electron sharing.
6. Which type of bond involves the sharing of electrons between atoms?
A) Ionic
B) Metallic
, C) Covalent
D) Hydrogen
Rationale: Covalent bonds form when atoms share electrons, commonly
between nonmetal atoms. Ionic bonding involves electron transfer rather
than sharing.
7. What is the chemical formula for water?
A) CO₂
B) O₂
C) H₂
D) H₂O
Rationale: A water molecule contains two hydrogen atoms covalently bonded
to one oxygen atom, giving it the formula H₂O.
8. Which substance is considered an acid?
A) NaOH
B) KOH
C) HCl
D) NaCl
Rationale: Hydrochloric acid (HCl) is a strong acid that dissociates extensively
in aqueous solution to produce hydrogen ions. NaOH and KOH are bases.
9. What is the pH of a neutral aqueous solution at 25°C?
A) 0
B) 7
C) 10
D) 14
Rationale: At 25°C, a neutral solution has equal concentrations of H⁺ and OH⁻
ions (1.0 × 10⁻⁷ M), resulting in a pH of exactly 7.
