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A LEVEL CHEMISTRY (OCR SPECIFICATION A - H432) PAPER 1 EXAM
QUESTIONS WITH DETAILED- VERIFIED ANSWERS- ALREADY
GRADED A+ || NEWEST EXAM
Chemistry
This OCR A Level Chemistry A Paper 1 (H432/01) practice exam covers:
Atomic Structure & Periodicity, Bonding & Structure, Energetics, Kinetics,
Equilibrium, Redox & Electrochemistry, Acids, Bases & Buffers,
Transition Metals, and Inorganic/Periodicity
Module 2: Foundations in chemistry (atomic structure, bonding, amount
of substance)
Module 3: Periodic table and energy (periodicity, energetics, kinetics,
equilibrium)
Module 5: Physical chemistry and transition elements (rates,
equilibrium, acids and bases, redox, transition metals)
SECTION 1: ATOMIC STRUCTURE & PERIODICITY
QUESTION 1
The table shows the number of protons and neutrons in four different
atoms.
Atom Number of protons Number of neutrons
W 17 18
X 18 18
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Y 17 19
Z 18 19
Which two atoms are isotopes of the same element?
A. W and X
B. X and Y
C. X and Z
D. Y and Z
Correct Answer: C. X and Z
Rationale: Isotopes are atoms of the same element with the same
number of protons but different numbers of neutrons. Atoms X and Z
both have 18 protons, identifying them as the same element (argon), with
18 and 19 neutrons respectively.
QUESTION 2
Which sample contains the greatest number of molecules?
A. 35 g of C₂H₂
B. 45 g of C₂H₆
C. 60 g of C₄H₁₀
D. 100 g of C₆H₆
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Correct Answer: D. 100 g of C₆H₆
Rationale: Number of molecules = mass / molar mass × Avogadro's
constant. C₆H₆ has the lowest molar mass (78 g mol⁻¹) among the
options relative to its mass. 100 g ÷ 78 = 1.28 mol, giving the greatest
number of molecules.
QUESTION 3
11.895 g of hydrated cobalt(II) chloride, CoCl₂·xH₂O, is heated to remove
the water of crystallisation. After heating to constant mass, the mass of
the anhydrous salt was 6.495 g. What is the value of x?
A. 3
B. 5
C. 6
D. 7
Correct Answer: C. 6
Rationale: Mass of water lost = 11.895 − 6.495 = 5.400 g. Moles of
anhydrous CoCl₂ = 6..9 = 0.0500 mol. Moles of water = 5.400 /
18.0 = 0.300 mol. Ratio H₂O:CoCl₂ = 0.300:0.0500 = 6:1, so x = 6.
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QUESTION 4
How many hydrogen atoms are in 2.00 g of pharmacolite,
CaHAsO₄·2H₂O?
A. 2.41 × 10²²
B. 4.82 × 10²²
C. 1.20 × 10²³
D. 2.41 × 10²³
Correct Answer: A. 2.41 × 10²²
Rationale: Molar mass of CaHAsO₄·2H₂O = 40.1 + 1.0 + 74.9 + 64.0 + 36.0
= 216.0 g mol⁻¹. Moles = 2..0 = 9.26 × 10⁻³ mol. Each formula unit
contains 5 H atoms (1 in CaHAsO₄ + 4 in 2H₂O). Total H atoms = 9.26 ×
10⁻³ × 5 × 6.02 × 10²³ = 2.79 × 10²² atoms.
QUESTION 5
Oxygen has the electron configuration 1s²2s²2p⁴. How many unpaired
electrons are present in a ground-state oxygen atom?
A. 0
B. 1
C. 2
A LEVEL CHEMISTRY (OCR SPECIFICATION A - H432) PAPER 1 EXAM
QUESTIONS WITH DETAILED- VERIFIED ANSWERS- ALREADY
GRADED A+ || NEWEST EXAM
Chemistry
This OCR A Level Chemistry A Paper 1 (H432/01) practice exam covers:
Atomic Structure & Periodicity, Bonding & Structure, Energetics, Kinetics,
Equilibrium, Redox & Electrochemistry, Acids, Bases & Buffers,
Transition Metals, and Inorganic/Periodicity
Module 2: Foundations in chemistry (atomic structure, bonding, amount
of substance)
Module 3: Periodic table and energy (periodicity, energetics, kinetics,
equilibrium)
Module 5: Physical chemistry and transition elements (rates,
equilibrium, acids and bases, redox, transition metals)
SECTION 1: ATOMIC STRUCTURE & PERIODICITY
QUESTION 1
The table shows the number of protons and neutrons in four different
atoms.
Atom Number of protons Number of neutrons
W 17 18
X 18 18
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Y 17 19
Z 18 19
Which two atoms are isotopes of the same element?
A. W and X
B. X and Y
C. X and Z
D. Y and Z
Correct Answer: C. X and Z
Rationale: Isotopes are atoms of the same element with the same
number of protons but different numbers of neutrons. Atoms X and Z
both have 18 protons, identifying them as the same element (argon), with
18 and 19 neutrons respectively.
QUESTION 2
Which sample contains the greatest number of molecules?
A. 35 g of C₂H₂
B. 45 g of C₂H₆
C. 60 g of C₄H₁₀
D. 100 g of C₆H₆
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Correct Answer: D. 100 g of C₆H₆
Rationale: Number of molecules = mass / molar mass × Avogadro's
constant. C₆H₆ has the lowest molar mass (78 g mol⁻¹) among the
options relative to its mass. 100 g ÷ 78 = 1.28 mol, giving the greatest
number of molecules.
QUESTION 3
11.895 g of hydrated cobalt(II) chloride, CoCl₂·xH₂O, is heated to remove
the water of crystallisation. After heating to constant mass, the mass of
the anhydrous salt was 6.495 g. What is the value of x?
A. 3
B. 5
C. 6
D. 7
Correct Answer: C. 6
Rationale: Mass of water lost = 11.895 − 6.495 = 5.400 g. Moles of
anhydrous CoCl₂ = 6..9 = 0.0500 mol. Moles of water = 5.400 /
18.0 = 0.300 mol. Ratio H₂O:CoCl₂ = 0.300:0.0500 = 6:1, so x = 6.
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QUESTION 4
How many hydrogen atoms are in 2.00 g of pharmacolite,
CaHAsO₄·2H₂O?
A. 2.41 × 10²²
B. 4.82 × 10²²
C. 1.20 × 10²³
D. 2.41 × 10²³
Correct Answer: A. 2.41 × 10²²
Rationale: Molar mass of CaHAsO₄·2H₂O = 40.1 + 1.0 + 74.9 + 64.0 + 36.0
= 216.0 g mol⁻¹. Moles = 2..0 = 9.26 × 10⁻³ mol. Each formula unit
contains 5 H atoms (1 in CaHAsO₄ + 4 in 2H₂O). Total H atoms = 9.26 ×
10⁻³ × 5 × 6.02 × 10²³ = 2.79 × 10²² atoms.
QUESTION 5
Oxygen has the electron configuration 1s²2s²2p⁴. How many unpaired
electrons are present in a ground-state oxygen atom?
A. 0
B. 1
C. 2
