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rOxford Cambridge and RSA
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34
A-Level OCR 2025 Chemistry A Paper 1
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Tuesday 10 June 2025 – Morning
43A Level Chemistry A
23H432/01 Periodic table, elements and physical chemistry
23Time allowed: 2 hours 15 minutes
1
Turn over
, 2
Section A
You should spend a maximum of 20 minutes on this section.
Write your answer to each question in the box provided.
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
Y 19 18
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
Your answer [1]
2 11.895 g of hydrated cobalt(II) chloride, CoCl 2•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
Your answer [1]
© OCR 2025
, 3
3 The diagram shows the Born-Haber cycle for sodium oxide, Na2O.
2Na+(g) + O2–(g)
2Na+(g) + O(g) + 2e–
2Na(g) + O(g) 2Na+(g) + O–(g) + e–
2Na(g) + ½O2(g)
2Na(s) + ½O2(g)
Na2O(s)
Why is the value for the second electron affinity of oxygen positive?
A An electron is added to a high energy orbital.
B An electron is added to a negative ion.
C An electron is removed from a gaseous atom.
D An electron is removed from a positive ion.
Your answer [1]
4 What volume, in cm3, of 0.250 mol dm–3 barium hydroxide solution is required to exactly
neutralise 25.0 cm3 of 0.115 mol dm–3 hydrochloric acid?
Ba(OH)2(aq) + 2HCl (aq) BaCl 2(aq) + 2H2O(l)
A 5.75
B 11.50
C 23.00
D 54.35
Your answer [1]
© OCR 2025 Turn over
, 4
5 The graph shows the volume of hydrogen released over time in a chemical reaction.
100
90
80
70
60
Volume of
hydrogen 50
/ cm3
40
30
20
10
0
0 20 40 60 80 100
Time / s
What is the rate of reaction, in cm3 s–1, at 30 seconds?
A 0.8
B 1.2
C 2.1
D 2.4
Your answer [1]
© OCR 2025
88888888888888883293gryxgxedggvgeveeexgr3g x
rOxford Cambridge and RSA
Gfdfghjkl;’jhgfdfghjkllkdsdfiio9866666666666666666555555555544444444444333333333322222222222222222
34
A-Level OCR 2025 Chemistry A Paper 1
Bdcxdzfrt5434344u7uhgvxe3ty6ytfdxsznn tg ryyt
Tuesday 10 June 2025 – Morning
43A Level Chemistry A
23H432/01 Periodic table, elements and physical chemistry
23Time allowed: 2 hours 15 minutes
1
Turn over
, 2
Section A
You should spend a maximum of 20 minutes on this section.
Write your answer to each question in the box provided.
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
Y 19 18
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
Your answer [1]
2 11.895 g of hydrated cobalt(II) chloride, CoCl 2•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
Your answer [1]
© OCR 2025
, 3
3 The diagram shows the Born-Haber cycle for sodium oxide, Na2O.
2Na+(g) + O2–(g)
2Na+(g) + O(g) + 2e–
2Na(g) + O(g) 2Na+(g) + O–(g) + e–
2Na(g) + ½O2(g)
2Na(s) + ½O2(g)
Na2O(s)
Why is the value for the second electron affinity of oxygen positive?
A An electron is added to a high energy orbital.
B An electron is added to a negative ion.
C An electron is removed from a gaseous atom.
D An electron is removed from a positive ion.
Your answer [1]
4 What volume, in cm3, of 0.250 mol dm–3 barium hydroxide solution is required to exactly
neutralise 25.0 cm3 of 0.115 mol dm–3 hydrochloric acid?
Ba(OH)2(aq) + 2HCl (aq) BaCl 2(aq) + 2H2O(l)
A 5.75
B 11.50
C 23.00
D 54.35
Your answer [1]
© OCR 2025 Turn over
, 4
5 The graph shows the volume of hydrogen released over time in a chemical reaction.
100
90
80
70
60
Volume of
hydrogen 50
/ cm3
40
30
20
10
0
0 20 40 60 80 100
Time / s
What is the rate of reaction, in cm3 s–1, at 30 seconds?
A 0.8
B 1.2
C 2.1
D 2.4
Your answer [1]
© OCR 2025
