HESI A2 Chemistry Practice Questions 150 QUESTIONS AND CORRECT
ANSWERS WITH RATIONALES 2026 LATEST VERSION NEEDED TO PASS
HESI A2 CHEMISTRY ENTRANCE EXAM
1. Which element is in Group 1 of the periodic table?
A) Calcium
B) Lithium
C) Oxygen
D) Fluorine
Rationale: Group 1 elements are alkali metals; lithium is one.
2. Which is a covalent compound?
A) NaCl
B) H₂O
C) KBr
D) MgO
Rationale: Covalent compounds form between nonmetals.
Diagram:
H-O-H
3. Which of the following is a polar molecule?
A) CO₂
B) H₂O
C) CH₄
D) O₂
Rationale: H₂O has a bent shape causing uneven electron distribution.
Diagram:
H
|
O--H
4. Which of these is a strong acid?
A) HCl
B) CH₃COOH
,C) H₂O
D) NH₃
Rationale: Strong acids dissociate completely in water.
5. What is the molar mass of CO₂?
A) 44 g/mol
B) 28 g/mol
C) 32 g/mol
D) 12 g/mol
Rationale: C = 12, O = 16×2 → 12+32 = 44 g/mol.
6. Which particle has a positive charge?
A) Electron
B) Neutron
C) Proton
D) Positron
Rationale: Protons are positively charged particles in the nucleus.
7. Which reaction is synthesis?
A) 2Na + Cl₂ → 2NaCl
B) H₂ + O₂ → H₂O₂
C) AB → A + B
D) Zn + HCl → ZnCl₂ + H₂
Rationale: Two reactants combine into one product.
8. Which of these elements is a halogen?
A) Sodium
B) Fluorine
C) Calcium
D) Oxygen
Rationale: Halogens are Group 17 elements.
9. Which solution is neutral?
A) HCl
B) NaOH
,C) Pure water
D) CH₃COOH
Rationale: Neutral solutions have pH = 7.
10. Which element has the highest electronegativity?
A) Fluorine
B) Oxygen
C) Nitrogen
D) Carbon
Rationale: Fluorine is the most electronegative element.
11. Which of these is a diatomic molecule?
A) He
B) H₂
C) Na
D) CO₂
Rationale: Some elements exist naturally as diatomic molecules: H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂.
12. What is the electron configuration of oxygen (O)?
A) 1s² 2s² 2p⁴
B) 1s² 2s² 2p⁶
C) 1s² 2s² 2p³
D) 1s² 2s² 2p⁵
Rationale: Oxygen has 8 electrons → 1s² 2s² 2p⁴.
13. Which of the following is a weak base?
A) NaOH
B) NH₃
C) KOH
D) Ba(OH)₂
Rationale: Weak bases partially dissociate in water.
14. Which compound contains a polyatomic ion?
A) NaCl
B) KNO₃
, C) Mg
D) H₂
Rationale: NO₃⁻ is a polyatomic ion.
15. Which of the following is a product of combustion of methane?
A) CO₂ and H₂O
B) NaCl
C) O₂
D) NH₃
Rationale: CH₄ + 2O₂ → CO₂ + 2H₂O
Diagram:
H H
\/
C
/\
H H
16. Which of the following is true about metals?
A) Poor conductors
B) Brittle
C) Malleable
D) Dull
Rationale: Metals are malleable, ductile, shiny, and good conductors.
17. Which of these reactions is decomposition?
A) AB → A + B
B) A + B → AB
C) C + O₂ → CO₂
D) Zn + HCl → ZnCl₂ + H₂
Rationale: A single compound breaks down into simpler substances.
18. Which of these is an exothermic process?
A) Photosynthesis
B) Melting ice
ANSWERS WITH RATIONALES 2026 LATEST VERSION NEEDED TO PASS
HESI A2 CHEMISTRY ENTRANCE EXAM
1. Which element is in Group 1 of the periodic table?
A) Calcium
B) Lithium
C) Oxygen
D) Fluorine
Rationale: Group 1 elements are alkali metals; lithium is one.
2. Which is a covalent compound?
A) NaCl
B) H₂O
C) KBr
D) MgO
Rationale: Covalent compounds form between nonmetals.
Diagram:
H-O-H
3. Which of the following is a polar molecule?
A) CO₂
B) H₂O
C) CH₄
D) O₂
Rationale: H₂O has a bent shape causing uneven electron distribution.
Diagram:
H
|
O--H
4. Which of these is a strong acid?
A) HCl
B) CH₃COOH
,C) H₂O
D) NH₃
Rationale: Strong acids dissociate completely in water.
5. What is the molar mass of CO₂?
A) 44 g/mol
B) 28 g/mol
C) 32 g/mol
D) 12 g/mol
Rationale: C = 12, O = 16×2 → 12+32 = 44 g/mol.
6. Which particle has a positive charge?
A) Electron
B) Neutron
C) Proton
D) Positron
Rationale: Protons are positively charged particles in the nucleus.
7. Which reaction is synthesis?
A) 2Na + Cl₂ → 2NaCl
B) H₂ + O₂ → H₂O₂
C) AB → A + B
D) Zn + HCl → ZnCl₂ + H₂
Rationale: Two reactants combine into one product.
8. Which of these elements is a halogen?
A) Sodium
B) Fluorine
C) Calcium
D) Oxygen
Rationale: Halogens are Group 17 elements.
9. Which solution is neutral?
A) HCl
B) NaOH
,C) Pure water
D) CH₃COOH
Rationale: Neutral solutions have pH = 7.
10. Which element has the highest electronegativity?
A) Fluorine
B) Oxygen
C) Nitrogen
D) Carbon
Rationale: Fluorine is the most electronegative element.
11. Which of these is a diatomic molecule?
A) He
B) H₂
C) Na
D) CO₂
Rationale: Some elements exist naturally as diatomic molecules: H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂.
12. What is the electron configuration of oxygen (O)?
A) 1s² 2s² 2p⁴
B) 1s² 2s² 2p⁶
C) 1s² 2s² 2p³
D) 1s² 2s² 2p⁵
Rationale: Oxygen has 8 electrons → 1s² 2s² 2p⁴.
13. Which of the following is a weak base?
A) NaOH
B) NH₃
C) KOH
D) Ba(OH)₂
Rationale: Weak bases partially dissociate in water.
14. Which compound contains a polyatomic ion?
A) NaCl
B) KNO₃
, C) Mg
D) H₂
Rationale: NO₃⁻ is a polyatomic ion.
15. Which of the following is a product of combustion of methane?
A) CO₂ and H₂O
B) NaCl
C) O₂
D) NH₃
Rationale: CH₄ + 2O₂ → CO₂ + 2H₂O
Diagram:
H H
\/
C
/\
H H
16. Which of the following is true about metals?
A) Poor conductors
B) Brittle
C) Malleable
D) Dull
Rationale: Metals are malleable, ductile, shiny, and good conductors.
17. Which of these reactions is decomposition?
A) AB → A + B
B) A + B → AB
C) C + O₂ → CO₂
D) Zn + HCl → ZnCl₂ + H₂
Rationale: A single compound breaks down into simpler substances.
18. Which of these is an exothermic process?
A) Photosynthesis
B) Melting ice
