CHEMISTRY HESI A2 ACTUAL EXAM 2026 |
QUESTIONS AND CORRECT DETAILED ANSWERS
WITH RATIONALE | ALREADY A GRADED | ALREADY
A GRADED | PDF
1. Which of the following is a noble gas?
A) Oxygen
B) Neon
C) Nitrogen
D) Hydrogen
Answer: B) Neon
Explanation: 👀 ** Noble gases are in Group 18 of the periodic table and are
inert, meaning they rarely react. Neon is a noble gas.
2. What is the molar mass of NaCl?
A) 35.45 g/mol
B) 58.44 g/mol
C) 22.99 g/mol
D) 40.00 g/mol
Answer: B) 58.44 g/mol
Explanation: 👀 ** Sodium (Na) = 22.99 g/mol, Chlorine (Cl) = 35.45 g/mol.
Add them: 22.99 + 35.45 = 58.44 g/mol.
,3. Which type of bond involves the sharing of electrons between atoms?
A) Ionic
B) Covalent
C) Metallic
D) Hydrogen
Answer: B) Covalent
Explanation: 👀 ** Covalent bonds involve sharing electrons between two
nonmetals. Ionic bonds involve transferring electrons.
4. What is the pH of a solution with [H⁺] = 1 × 10⁻³ M?
A) 3
B) 7
C) 11
D) 0
Answer: A) 3
Explanation: 👀 ** pH = -log[H⁺] → pH = -log(1 × 10⁻³) = 3.
5. Which element has 12 protons?
A) Carbon
B) Magnesium
C) Aluminum
D) Sodium
Answer: B) Magnesium
Explanation: 👀 ** The number of protons equals the atomic number.
Magnesium’s atomic number is 12.
,6. What is the chemical formula for sulfuric acid?
A) HCl
B) H₂SO₄
C) HNO₃
D) NaOH
Answer: B) H₂SO₄
Explanation: 👀 ** Sulfuric acid contains 2 hydrogen atoms, 1 sulfur, and 4
oxygen atoms → H₂SO₄.
7. A solution contains 0.5 moles of solute in 2 liters of solution. What is its
molarity?
A) 0.25 M
B) 1 M
C) 2 M
D) 4 M
Answer: A) 0.25 M
Explanation: 👀 ** Molarity = moles/volume (L). 0.5 ÷ 2 = 0.25 M.
8. Which of the following is an exothermic reaction?
A) Melting ice
B) Condensation of water vapor
C) Boiling water
D) Evaporation of alcohol
Answer: B) Condensation of water vapor
Explanation: 👀 ** Exothermic reactions release heat. Condensation releases
heat to the surroundings.
, 9. The chemical symbol “Fe” stands for which element?
A) Fluorine
B) Iron
C) Francium
D) Fermium
Answer: B) Iron
Explanation: 👀 ** Fe comes from the Latin “Ferrum,” meaning iron.
10. Which of these compounds is ionic?
A) CO₂
B) NaBr
C) CH₄
D) H₂O
Answer: B) NaBr
Explanation: 👀 ** Ionic compounds form between metals and nonmetals.
NaBr is sodium (metal) + bromine (nonmetal).
11. Which subatomic particle has a negative charge?
A) Proton
B) Neutron
C) Electron
D) Positron
Answer: C) Electron
Explanation: 👀 ** Electrons carry a negative charge, protons are positive, and
neutrons are neutral.
12. What is the electron configuration of oxygen (atomic number 8)?
A) 1s² 2s² 2p⁴
B) 1s² 2s² 2p⁶
QUESTIONS AND CORRECT DETAILED ANSWERS
WITH RATIONALE | ALREADY A GRADED | ALREADY
A GRADED | PDF
1. Which of the following is a noble gas?
A) Oxygen
B) Neon
C) Nitrogen
D) Hydrogen
Answer: B) Neon
Explanation: 👀 ** Noble gases are in Group 18 of the periodic table and are
inert, meaning they rarely react. Neon is a noble gas.
2. What is the molar mass of NaCl?
A) 35.45 g/mol
B) 58.44 g/mol
C) 22.99 g/mol
D) 40.00 g/mol
Answer: B) 58.44 g/mol
Explanation: 👀 ** Sodium (Na) = 22.99 g/mol, Chlorine (Cl) = 35.45 g/mol.
Add them: 22.99 + 35.45 = 58.44 g/mol.
,3. Which type of bond involves the sharing of electrons between atoms?
A) Ionic
B) Covalent
C) Metallic
D) Hydrogen
Answer: B) Covalent
Explanation: 👀 ** Covalent bonds involve sharing electrons between two
nonmetals. Ionic bonds involve transferring electrons.
4. What is the pH of a solution with [H⁺] = 1 × 10⁻³ M?
A) 3
B) 7
C) 11
D) 0
Answer: A) 3
Explanation: 👀 ** pH = -log[H⁺] → pH = -log(1 × 10⁻³) = 3.
5. Which element has 12 protons?
A) Carbon
B) Magnesium
C) Aluminum
D) Sodium
Answer: B) Magnesium
Explanation: 👀 ** The number of protons equals the atomic number.
Magnesium’s atomic number is 12.
,6. What is the chemical formula for sulfuric acid?
A) HCl
B) H₂SO₄
C) HNO₃
D) NaOH
Answer: B) H₂SO₄
Explanation: 👀 ** Sulfuric acid contains 2 hydrogen atoms, 1 sulfur, and 4
oxygen atoms → H₂SO₄.
7. A solution contains 0.5 moles of solute in 2 liters of solution. What is its
molarity?
A) 0.25 M
B) 1 M
C) 2 M
D) 4 M
Answer: A) 0.25 M
Explanation: 👀 ** Molarity = moles/volume (L). 0.5 ÷ 2 = 0.25 M.
8. Which of the following is an exothermic reaction?
A) Melting ice
B) Condensation of water vapor
C) Boiling water
D) Evaporation of alcohol
Answer: B) Condensation of water vapor
Explanation: 👀 ** Exothermic reactions release heat. Condensation releases
heat to the surroundings.
, 9. The chemical symbol “Fe” stands for which element?
A) Fluorine
B) Iron
C) Francium
D) Fermium
Answer: B) Iron
Explanation: 👀 ** Fe comes from the Latin “Ferrum,” meaning iron.
10. Which of these compounds is ionic?
A) CO₂
B) NaBr
C) CH₄
D) H₂O
Answer: B) NaBr
Explanation: 👀 ** Ionic compounds form between metals and nonmetals.
NaBr is sodium (metal) + bromine (nonmetal).
11. Which subatomic particle has a negative charge?
A) Proton
B) Neutron
C) Electron
D) Positron
Answer: C) Electron
Explanation: 👀 ** Electrons carry a negative charge, protons are positive, and
neutrons are neutral.
12. What is the electron configuration of oxygen (atomic number 8)?
A) 1s² 2s² 2p⁴
B) 1s² 2s² 2p⁶
