HESI A2 Chemistry ACTUAL EXAM 150 QUESTIONS AND CORRECT
ANSWERS WITH DETAILED RATIONALRES 2026 LATEST VERSION ALL
NEEDED TO PASS HESI A2 CHEMISTRY EXAM
1. Which of the following is the correct chemical symbol for potassium?
A) P
B) Po
C) K
D) Pt
Rationale: Potassium has the symbol K from the Latin word kalium. P is phosphorus, Po is polonium, Pt
is platinum.
2. What is the atomic number of carbon?
A) 6
B) 12
C) 14
D) 8
Rationale: The atomic number represents the number of protons. Carbon has 6 protons.
3. Which of the following is an example of a chemical change?
A) Ice melting
B) Paper burning
C) Sugar dissolving in water
D) Boiling water
Rationale: A chemical change produces a new substance. Burning paper changes it into ash, CO₂, and
water vapor. Melting and dissolving are physical changes.
4. The chemical formula H₂SO₄ represents:
A) Hydrochloric acid
B) Sulfuric acid
C) Nitric acid
D) Sodium hydroxide
Rationale: H₂SO₄ is sulfuric acid, a strong acid used in batteries and chemical synthesis.
,5. What is the molar mass of H₂O?
A) 16 g/mol
B) 18 g/mol
C) 20 g/mol
D) 22 g/mol
Rationale: H₂O contains 2 hydrogen atoms (1 g/mol each) and 1 oxygen atom (16 g/mol): 2 + 16 = 18
g/mol.
6. Which subatomic particle has a negative charge?
A) Proton
B) Neutron
C) Electron
D) Nucleus
Rationale: Electrons are negatively charged, protons positive, neutrons neutral.
7. How many valence electrons does oxygen have?
A) 2
B) 4
C) 6
D) 8
Rationale: Oxygen is in Group 16 of the periodic table and has 6 electrons in its outer shell.
8. Which type of bond is formed when electrons are shared between atoms?
A) Ionic
B) Covalent
C) Metallic
D) Hydrogen
Rationale: Covalent bonds involve sharing electrons, while ionic bonds transfer electrons.
9. Identify the following molecule: CH₄
A) Methane
B) Ethane
C) Propane
D) Carbon monoxide
Rationale: CH₄ has one carbon atom and four hydrogen atoms, which is methane, a simple
hydrocarbon.
,10. What is the pH of a neutral solution at 25°C?
A) 0
B) 7
C) 14
D) 1
Rationale: Neutral solutions (like pure water) have a pH of 7, acidic <7, basic >7.
11. Which element is a halogen?
A) Oxygen
B) Chlorine
C) Sodium
D) Calcium
Rationale: Halogens are Group 17 elements. Chlorine is a halogen; oxygen is a nonmetal, sodium and
calcium are metals.
12. What is the chemical formula for table salt?
A) NaCl
B) KCl
C) Na₂CO₃
D) HCl
Rationale: Table salt is sodium chloride (NaCl).
13. Which gas is produced when acids react with metals like zinc?
A) Oxygen
B) Hydrogen
C) Carbon dioxide
D) Nitrogen
Rationale: Reaction of acids with metals produces hydrogen gas. Example: Zn + 2HCl → ZnCl₂ + H₂.
14. How many protons are in an atom of nitrogen?
A) 5
B) 7
C) 14
D) 10
Rationale: Nitrogen has atomic number 7, which means 7 protons.
, 15. What is the main difference between an ionic and a covalent bond?
A) Ionic shares electrons, covalent transfers electrons
B) Ionic transfers electrons, covalent shares electrons
C) Ionic occurs between nonmetals only
D) Covalent forms salts
Rationale: Ionic bonds transfer electrons (metal + nonmetal), covalent share electrons (nonmetal +
nonmetal).
16. Which state of matter has a definite volume but no definite shape?
A) Solid
B) Liquid
C) Gas
D) Plasma
Rationale: Liquids take the shape of their container but maintain definite volume.
17. What is the mass number of an atom with 12 protons and 14 neutrons?
A) 12
B) 14
C) 26
D) 28
Rationale: Mass number = protons + neutrons → 12 + 14 = 26.
18. Which particle determines the identity of an element?
A) Proton
B) Neutron
C) Electron
D) Neutrino
Rationale: The number of protons defines the element.
19. Which of the following is a strong acid?
A) HCl
B) CH₃COOH
C) H₂CO₃
D) NH₄OH
ANSWERS WITH DETAILED RATIONALRES 2026 LATEST VERSION ALL
NEEDED TO PASS HESI A2 CHEMISTRY EXAM
1. Which of the following is the correct chemical symbol for potassium?
A) P
B) Po
C) K
D) Pt
Rationale: Potassium has the symbol K from the Latin word kalium. P is phosphorus, Po is polonium, Pt
is platinum.
2. What is the atomic number of carbon?
A) 6
B) 12
C) 14
D) 8
Rationale: The atomic number represents the number of protons. Carbon has 6 protons.
3. Which of the following is an example of a chemical change?
A) Ice melting
B) Paper burning
C) Sugar dissolving in water
D) Boiling water
Rationale: A chemical change produces a new substance. Burning paper changes it into ash, CO₂, and
water vapor. Melting and dissolving are physical changes.
4. The chemical formula H₂SO₄ represents:
A) Hydrochloric acid
B) Sulfuric acid
C) Nitric acid
D) Sodium hydroxide
Rationale: H₂SO₄ is sulfuric acid, a strong acid used in batteries and chemical synthesis.
,5. What is the molar mass of H₂O?
A) 16 g/mol
B) 18 g/mol
C) 20 g/mol
D) 22 g/mol
Rationale: H₂O contains 2 hydrogen atoms (1 g/mol each) and 1 oxygen atom (16 g/mol): 2 + 16 = 18
g/mol.
6. Which subatomic particle has a negative charge?
A) Proton
B) Neutron
C) Electron
D) Nucleus
Rationale: Electrons are negatively charged, protons positive, neutrons neutral.
7. How many valence electrons does oxygen have?
A) 2
B) 4
C) 6
D) 8
Rationale: Oxygen is in Group 16 of the periodic table and has 6 electrons in its outer shell.
8. Which type of bond is formed when electrons are shared between atoms?
A) Ionic
B) Covalent
C) Metallic
D) Hydrogen
Rationale: Covalent bonds involve sharing electrons, while ionic bonds transfer electrons.
9. Identify the following molecule: CH₄
A) Methane
B) Ethane
C) Propane
D) Carbon monoxide
Rationale: CH₄ has one carbon atom and four hydrogen atoms, which is methane, a simple
hydrocarbon.
,10. What is the pH of a neutral solution at 25°C?
A) 0
B) 7
C) 14
D) 1
Rationale: Neutral solutions (like pure water) have a pH of 7, acidic <7, basic >7.
11. Which element is a halogen?
A) Oxygen
B) Chlorine
C) Sodium
D) Calcium
Rationale: Halogens are Group 17 elements. Chlorine is a halogen; oxygen is a nonmetal, sodium and
calcium are metals.
12. What is the chemical formula for table salt?
A) NaCl
B) KCl
C) Na₂CO₃
D) HCl
Rationale: Table salt is sodium chloride (NaCl).
13. Which gas is produced when acids react with metals like zinc?
A) Oxygen
B) Hydrogen
C) Carbon dioxide
D) Nitrogen
Rationale: Reaction of acids with metals produces hydrogen gas. Example: Zn + 2HCl → ZnCl₂ + H₂.
14. How many protons are in an atom of nitrogen?
A) 5
B) 7
C) 14
D) 10
Rationale: Nitrogen has atomic number 7, which means 7 protons.
, 15. What is the main difference between an ionic and a covalent bond?
A) Ionic shares electrons, covalent transfers electrons
B) Ionic transfers electrons, covalent shares electrons
C) Ionic occurs between nonmetals only
D) Covalent forms salts
Rationale: Ionic bonds transfer electrons (metal + nonmetal), covalent share electrons (nonmetal +
nonmetal).
16. Which state of matter has a definite volume but no definite shape?
A) Solid
B) Liquid
C) Gas
D) Plasma
Rationale: Liquids take the shape of their container but maintain definite volume.
17. What is the mass number of an atom with 12 protons and 14 neutrons?
A) 12
B) 14
C) 26
D) 28
Rationale: Mass number = protons + neutrons → 12 + 14 = 26.
18. Which particle determines the identity of an element?
A) Proton
B) Neutron
C) Electron
D) Neutrino
Rationale: The number of protons defines the element.
19. Which of the following is a strong acid?
A) HCl
B) CH₃COOH
C) H₂CO₃
D) NH₄OH
