ACS CHEMISTRY GENERAL EXAM 2025
ACTUAL EXAM COMPLETE QUESTIONS WITH
DETAILED VERIFIED ANSWERS /ALREADY
GRADED A+
Questions and answers
Atomic Structure & Periodicity
• Q1. Which orbital can hold a maximum of 10 electrons?
A. s
B. p
C. d
D. f
Answer: C. d – s=2, p=6, d=10, f=14.
• Q2. Which atom has the largest atomic radius?
A. Li
B. Na
C. K
D. Rb
Answer: D. Rb – Radius increases down a group.
• Q3. Which ion has the same electron configuration as Ne?
A. F⁻
B. Na⁺
C. O²⁻
, D. All of the above
Answer: D – All reach 1s²2s²2p⁶ (10 e⁻).
• Q4. Which has the highest electronegativity?
A. C
B. O
C. N
D. F
Answer: D. F – Fluorine is most electronegative.
• Q5. The number of unpaired electrons in ground-state oxygen is:
A. 0
B. 1
C. 2
D. 4
Answer: C. 2 – Oxygen: 1s²2s²2p⁴ → two unpaired p electrons.
•
• Bonding & Structure
• Q6. Which molecule is linear?
A. CO₂
B. H₂O
C. SO₂
D. O₃
Answer: A. CO₂ – O=C=O is linear, rest bent.
• Q7. Which has resonance structures?
A. CH₄
B. H₂O
C. NO₃⁻
D. NH₃
Answer: C. NO₃⁻ – Resonance among three O atoms.
• Q8. The bond angle in CH₄ is:
A. 90°
B. 107°
C. 109.5°
, D. 120°
Answer: C. 109.5° – Tetrahedral geometry.
• Q9. Which bond is most polar?
A. C–H
B. C–O
C. O–H
D. N–H
Answer: C. O–H – Biggest ΔEN difference.
• Q10. The hybridization of carbon in HCN is:
A. sp
B. sp²
C. sp³
D. None
Answer: A. sp – Triple bond → linear.
•
• Stoichiometry & Reactions
• Q11. How many moles of O₂ are needed to combust 2 mol CH₄?
CH₄ + 2 O₂ → CO₂ + 2 H₂O
A. 2
B. 3
C. 4
D. 6
Answer: C. 4 – 2 CH₄ × 2 O₂/1 CH₄ = 4.
• Q12. Percent composition of oxygen in H₂O?
A. 11%
B. 33%
C. 67%
D. 89%
Answer: D. 89% – (16/18) × 100.
• Q13. A 10 g sample of CaCO₃ decomposes completely. How many
grams of CO₂ are produced?
CaCO₃ → CaO + CO₂
, A. 2.2 g
B. 4.4 g
C. 6.6 g
D. 10 g
Answer: B. 4.4 g – 44/100 g ratio.
• Q14. In a redox reaction, the oxidizing agent is:
A. The species oxidized
B. The species reduced
C. Always oxygen
D. Always hydrogen
Answer: B. The species reduced – It causes oxidation of the
other.
• Q15. Which is a strong electrolyte?
A. NaCl(aq)
B. HF(aq)
C. NH₃(aq)
D. CH₃OH(aq)
Answer: A. NaCl – Strong electrolyte = strong acid/base or
soluble salt.
•
• States of Matter
• Q16. At STP, 1 mol of any ideal gas occupies:
A. 11.2 L
B. 22.4 L
C. 24.0 L
D. 1.0 L
Answer: B. 22.4 L
• Q17. Which gas effuses fastest?
A. O₂
B. N₂
C. He
ACTUAL EXAM COMPLETE QUESTIONS WITH
DETAILED VERIFIED ANSWERS /ALREADY
GRADED A+
Questions and answers
Atomic Structure & Periodicity
• Q1. Which orbital can hold a maximum of 10 electrons?
A. s
B. p
C. d
D. f
Answer: C. d – s=2, p=6, d=10, f=14.
• Q2. Which atom has the largest atomic radius?
A. Li
B. Na
C. K
D. Rb
Answer: D. Rb – Radius increases down a group.
• Q3. Which ion has the same electron configuration as Ne?
A. F⁻
B. Na⁺
C. O²⁻
, D. All of the above
Answer: D – All reach 1s²2s²2p⁶ (10 e⁻).
• Q4. Which has the highest electronegativity?
A. C
B. O
C. N
D. F
Answer: D. F – Fluorine is most electronegative.
• Q5. The number of unpaired electrons in ground-state oxygen is:
A. 0
B. 1
C. 2
D. 4
Answer: C. 2 – Oxygen: 1s²2s²2p⁴ → two unpaired p electrons.
•
• Bonding & Structure
• Q6. Which molecule is linear?
A. CO₂
B. H₂O
C. SO₂
D. O₃
Answer: A. CO₂ – O=C=O is linear, rest bent.
• Q7. Which has resonance structures?
A. CH₄
B. H₂O
C. NO₃⁻
D. NH₃
Answer: C. NO₃⁻ – Resonance among three O atoms.
• Q8. The bond angle in CH₄ is:
A. 90°
B. 107°
C. 109.5°
, D. 120°
Answer: C. 109.5° – Tetrahedral geometry.
• Q9. Which bond is most polar?
A. C–H
B. C–O
C. O–H
D. N–H
Answer: C. O–H – Biggest ΔEN difference.
• Q10. The hybridization of carbon in HCN is:
A. sp
B. sp²
C. sp³
D. None
Answer: A. sp – Triple bond → linear.
•
• Stoichiometry & Reactions
• Q11. How many moles of O₂ are needed to combust 2 mol CH₄?
CH₄ + 2 O₂ → CO₂ + 2 H₂O
A. 2
B. 3
C. 4
D. 6
Answer: C. 4 – 2 CH₄ × 2 O₂/1 CH₄ = 4.
• Q12. Percent composition of oxygen in H₂O?
A. 11%
B. 33%
C. 67%
D. 89%
Answer: D. 89% – (16/18) × 100.
• Q13. A 10 g sample of CaCO₃ decomposes completely. How many
grams of CO₂ are produced?
CaCO₃ → CaO + CO₂
, A. 2.2 g
B. 4.4 g
C. 6.6 g
D. 10 g
Answer: B. 4.4 g – 44/100 g ratio.
• Q14. In a redox reaction, the oxidizing agent is:
A. The species oxidized
B. The species reduced
C. Always oxygen
D. Always hydrogen
Answer: B. The species reduced – It causes oxidation of the
other.
• Q15. Which is a strong electrolyte?
A. NaCl(aq)
B. HF(aq)
C. NH₃(aq)
D. CH₃OH(aq)
Answer: A. NaCl – Strong electrolyte = strong acid/base or
soluble salt.
•
• States of Matter
• Q16. At STP, 1 mol of any ideal gas occupies:
A. 11.2 L
B. 22.4 L
C. 24.0 L
D. 1.0 L
Answer: B. 22.4 L
• Q17. Which gas effuses fastest?
A. O₂
B. N₂
C. He
