AQA AS Level Chemistry Paper 1 LATEST 2025 WITH
QUESTIONS AND CORRECT VERIFIED ANSWERS
GRADED A+ GUARANTEED PASS**100/100**Updated!!
Section A: Multiple Choice (30 questions)
Q1. Which sample contains the greatest number of atoms?
A) 1.0 g of helium
B) 1.0 g of methane (CH₄)
C) 1.0 g of water
D) 1.0 g of carbon dioxide
Answer: A
Rationale: Number of atoms = (mass / Mᵣ) × (atoms per molecule) × Avogadro’s constant.
• He: (1/4) × 1 = 0.25 mol atoms
• CH₄: (1/16) × 5 = 0.3125 mol atoms
• H₂O: (1/18) × 3 ≈ 0.1667 mol atoms
• CO₂: (1/44) × 3 ≈ 0.0682 mol atoms
Methane has the highest moles of atoms, but check – He (0.25), CH₄ (0.3125) → CH₄
has more. Wait – I need to correct: The question asks “greatest number of atoms” –
let’s recalc carefully:
1g He = 1/4 = 0.25 mol He atoms = 0.25 × N_A atoms.
1g CH₄ = 1/16 = 0.0625 mol molecules × 5 atoms/molecule = 0.3125 mol atoms.
1g H₂O = 1/18 ≈ 0.0556 mol × 3 = 0.1667 mol atoms.
1g CO₂ = 1/44 ≈ 0.0227 mol × 3 = 0.0681 mol atoms.
So CH₄ has most atoms. Answer = B.
Correction to original marking: B is correct, not A.
,Q2. Which ion has the electron configuration 1s² 2s² 2p⁶?
A) Na⁺
B) Mg²⁺
C) O²⁻
D) All of the above
Answer: D
Rationale: Neon configuration (10 electrons). Na⁺ (11-1=10), Mg²⁺ (12-2=10), O²⁻ (8+2=10).
All are isoelectronic with Ne.
Q3. Which molecule has a bent shape?
A) CO₂
B) BF₃
C) H₂O
D) CH₄
Answer: C
Rationale: H₂O has two bonding pairs and two lone pairs on oxygen → tetrahedral electron
geometry, bent molecular shape (bond angle ~104.5°).
Q4. What is the relative atomic mass of an element with two isotopes: 35 amu (75%) and 37
amu (25%)?
A) 35.0
B) 35.5
C) 36.0
D) 37.0
Answer: B
Rationale: (35×0.75) + (37×0.25) = 26.25 + 9.25 = 35.5 amu.
Q5. Which compound contains both ionic and covalent bonds?
A) NaCl
B) MgO
C) NH₄Cl
D) CCl₄
, Answer: C
Rationale: NH₄Cl has NH₄⁺ (covalent N-H bonds) and Cl⁻ (ionic bond between NH₄⁺ and Cl⁻).
Q6. Which element has the highest first ionisation energy?
A) Li
B) Be
C) B
D) C
Answer: B (Be)
Rationale: Be (1s²2s²) has a full 2s subshell, requiring more energy to remove an electron
than B (1s²2s²2p¹) where the 2p electron is easier to remove due to higher energy and
shielding.
Q7. What is the oxidation state of sulfur in H₂SO₄?
A) +2
B) +4
C) +6
D) -2
Answer: C
Rationale: H = +1 (×2 = +2), O = -2 (×4 = -8), so S + 2 - 8 = 0 → S = +6.
Q8. Which reaction is a redox reaction?
A) AgNO₃ + NaCl → AgCl + NaNO₃
B) CaO + CO₂ → CaCO₃
C) Zn + CuSO₄ → ZnSO₄ + Cu
D) NaOH + HCl → NaCl + H₂O
Answer: C
Rationale: Zn (0) → Zn²⁺ (+2) oxidised; Cu²⁺ (+2) → Cu (0) reduced. Oxidation states change.
Q9. What is the mass of 0.250 mol of Na₂CO₃? (Mᵣ = 106)
A) 26.5 g
B) 53.0 g
QUESTIONS AND CORRECT VERIFIED ANSWERS
GRADED A+ GUARANTEED PASS**100/100**Updated!!
Section A: Multiple Choice (30 questions)
Q1. Which sample contains the greatest number of atoms?
A) 1.0 g of helium
B) 1.0 g of methane (CH₄)
C) 1.0 g of water
D) 1.0 g of carbon dioxide
Answer: A
Rationale: Number of atoms = (mass / Mᵣ) × (atoms per molecule) × Avogadro’s constant.
• He: (1/4) × 1 = 0.25 mol atoms
• CH₄: (1/16) × 5 = 0.3125 mol atoms
• H₂O: (1/18) × 3 ≈ 0.1667 mol atoms
• CO₂: (1/44) × 3 ≈ 0.0682 mol atoms
Methane has the highest moles of atoms, but check – He (0.25), CH₄ (0.3125) → CH₄
has more. Wait – I need to correct: The question asks “greatest number of atoms” –
let’s recalc carefully:
1g He = 1/4 = 0.25 mol He atoms = 0.25 × N_A atoms.
1g CH₄ = 1/16 = 0.0625 mol molecules × 5 atoms/molecule = 0.3125 mol atoms.
1g H₂O = 1/18 ≈ 0.0556 mol × 3 = 0.1667 mol atoms.
1g CO₂ = 1/44 ≈ 0.0227 mol × 3 = 0.0681 mol atoms.
So CH₄ has most atoms. Answer = B.
Correction to original marking: B is correct, not A.
,Q2. Which ion has the electron configuration 1s² 2s² 2p⁶?
A) Na⁺
B) Mg²⁺
C) O²⁻
D) All of the above
Answer: D
Rationale: Neon configuration (10 electrons). Na⁺ (11-1=10), Mg²⁺ (12-2=10), O²⁻ (8+2=10).
All are isoelectronic with Ne.
Q3. Which molecule has a bent shape?
A) CO₂
B) BF₃
C) H₂O
D) CH₄
Answer: C
Rationale: H₂O has two bonding pairs and two lone pairs on oxygen → tetrahedral electron
geometry, bent molecular shape (bond angle ~104.5°).
Q4. What is the relative atomic mass of an element with two isotopes: 35 amu (75%) and 37
amu (25%)?
A) 35.0
B) 35.5
C) 36.0
D) 37.0
Answer: B
Rationale: (35×0.75) + (37×0.25) = 26.25 + 9.25 = 35.5 amu.
Q5. Which compound contains both ionic and covalent bonds?
A) NaCl
B) MgO
C) NH₄Cl
D) CCl₄
, Answer: C
Rationale: NH₄Cl has NH₄⁺ (covalent N-H bonds) and Cl⁻ (ionic bond between NH₄⁺ and Cl⁻).
Q6. Which element has the highest first ionisation energy?
A) Li
B) Be
C) B
D) C
Answer: B (Be)
Rationale: Be (1s²2s²) has a full 2s subshell, requiring more energy to remove an electron
than B (1s²2s²2p¹) where the 2p electron is easier to remove due to higher energy and
shielding.
Q7. What is the oxidation state of sulfur in H₂SO₄?
A) +2
B) +4
C) +6
D) -2
Answer: C
Rationale: H = +1 (×2 = +2), O = -2 (×4 = -8), so S + 2 - 8 = 0 → S = +6.
Q8. Which reaction is a redox reaction?
A) AgNO₃ + NaCl → AgCl + NaNO₃
B) CaO + CO₂ → CaCO₃
C) Zn + CuSO₄ → ZnSO₄ + Cu
D) NaOH + HCl → NaCl + H₂O
Answer: C
Rationale: Zn (0) → Zn²⁺ (+2) oxidised; Cu²⁺ (+2) → Cu (0) reduced. Oxidation states change.
Q9. What is the mass of 0.250 mol of Na₂CO₃? (Mᵣ = 106)
A) 26.5 g
B) 53.0 g
