OCR AS LEVEL CHEMISTRY A JUNE 2026 PAPER 1: BREADTH IN CHEMISTRY PRACTICE
EXAM
SECTION A: MULTIPLE CHOICE (Questions 1–30)
1. Which particle has the same electron configuration as a fluoride ion, F⁻?
A. Ne
B. Na⁺
C. O²⁻
D. Mg²⁺
Answer: B
Rationale: F⁻ has 10 electrons. Na⁺ also has 10 electrons (11 protons minus 1 electron).
Ne has 10 electrons but is a neutral atom, not isoelectronic in the same ionic sense being
tested here. O²⁻ also has 10 electrons but Na⁺ is the most direct comparison among the
choices given the context of common ions.
2. What is the shape of a molecule of sulfur hexafluoride, SF₆?
A. Trigonal bipyramidal
B. Octahedral
C. Tetrahedral
D. Square planar
Answer: B
, Rationale: Sulfur in SF₆ has six bonding pairs and zero lone pairs. According to VSEPR
theory, six bonding pairs arrange themselves octahedrally to minimise repulsion.
3. Which of the following is the correct definition of first ionisation energy?
A. The energy required to remove one electron from each atom in one mole of gaseous
atoms.
B. The energy required to remove one mole of electrons from one mole of gaseous ions.
C. The energy released when one mole of gaseous atoms gains one mole of electrons.
D. The energy required to remove one electron from a gaseous atom.
Answer: A
Rationale: First ionisation energy is defined per mole of gaseous atoms, not per single
atom. Option D is insufficiently precise as it omits the "one mole" standard quantity.
4. How many moles of ions are present in 2.00 mol of magnesium chloride, MgCl₂?
A. 2.00 mol
B. 4.00 mol
C. 6.00 mol
D. 8.00 mol
Answer: C
Rationale: Each formula unit of MgCl₂ produces one Mg²⁺ ion and two Cl⁻ ions, totalling
three ions. Therefore, 2.00 mol × 3 = 6.00 mol of ions.
5. What is the oxidation number of chromium in the dichromate ion, Cr₂O₇²⁻?
A. +3
B. +5
C. +6
D. +7
Answer: C
Rationale: Oxygen contributes −2 per atom, giving −14 total. The overall charge is −2. Let Cr
= x: 2x + (−14) = −2, so 2x = +12, x = +6.
EXAM
SECTION A: MULTIPLE CHOICE (Questions 1–30)
1. Which particle has the same electron configuration as a fluoride ion, F⁻?
A. Ne
B. Na⁺
C. O²⁻
D. Mg²⁺
Answer: B
Rationale: F⁻ has 10 electrons. Na⁺ also has 10 electrons (11 protons minus 1 electron).
Ne has 10 electrons but is a neutral atom, not isoelectronic in the same ionic sense being
tested here. O²⁻ also has 10 electrons but Na⁺ is the most direct comparison among the
choices given the context of common ions.
2. What is the shape of a molecule of sulfur hexafluoride, SF₆?
A. Trigonal bipyramidal
B. Octahedral
C. Tetrahedral
D. Square planar
Answer: B
, Rationale: Sulfur in SF₆ has six bonding pairs and zero lone pairs. According to VSEPR
theory, six bonding pairs arrange themselves octahedrally to minimise repulsion.
3. Which of the following is the correct definition of first ionisation energy?
A. The energy required to remove one electron from each atom in one mole of gaseous
atoms.
B. The energy required to remove one mole of electrons from one mole of gaseous ions.
C. The energy released when one mole of gaseous atoms gains one mole of electrons.
D. The energy required to remove one electron from a gaseous atom.
Answer: A
Rationale: First ionisation energy is defined per mole of gaseous atoms, not per single
atom. Option D is insufficiently precise as it omits the "one mole" standard quantity.
4. How many moles of ions are present in 2.00 mol of magnesium chloride, MgCl₂?
A. 2.00 mol
B. 4.00 mol
C. 6.00 mol
D. 8.00 mol
Answer: C
Rationale: Each formula unit of MgCl₂ produces one Mg²⁺ ion and two Cl⁻ ions, totalling
three ions. Therefore, 2.00 mol × 3 = 6.00 mol of ions.
5. What is the oxidation number of chromium in the dichromate ion, Cr₂O₇²⁻?
A. +3
B. +5
C. +6
D. +7
Answer: C
Rationale: Oxygen contributes −2 per atom, giving −14 total. The overall charge is −2. Let Cr
= x: 2x + (−14) = −2, so 2x = +12, x = +6.
