Oxford Cambridge and RSA
*1327955883*
Tuesday 21 May 2025 – Morning
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 20 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2024 [601/5256/4] DC (PQ/SG) 334107/3
OCR is an exempt Charity
Turn over
1 This question is about water, H2O, and ammonia, NH3.
, 2
(a) Hydrogen and oxygen have different electronegativities.
What is meant by the term electronegativity?
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
............. [2]
(b) H2O is a polar molecule that has hydrogen bonding.
(i) Complete the diagram below to show hydrogen bonding between the H 2O molecule
shown and another H2O molecule.
Include relevant dipoles and lone pairs.
Label the hydrogen bond.
O
H H
(ii) Explain why molecules of H2O are polar.
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
............. [1]
(iii) One unusual property of H2O is that ice floats on water.
Explain why ice has a lower density than water.
........................................................................................................................................
..................
© OCR 2024
, 3
........................................................................................................................................
..................
........................................................................................................................................
............. [1]
(c) Solid ammonia, NH3, also contains hydrogen bonds.
(i) Suggest why solid ammonia has a lower melting point than ice.
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
............. [2]
(ii) When ammonia dissolves in water, ammonium ions, NH4+, are formed.
Draw a ‘dot-and-cross’ diagram to show the bonding in an NH4+ ion.
Show outer electrons only.
(iii) Outline how you would test for the presence of NH4+ ions in a solution.
Your answer should include observations.
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
............. [2]
© OCR 2024 Turn over
, 4
(d) A student heats 11.50 g of hydrated zinc sulfate, ZnSO 4•7H2O, to remove all the water
of crystallisation.
Calculate the mass of anhydrous zinc sulfate that should be obtained.
mass = ....................................................... g [3] 2 This question is about
periodicity and the reaction of some Group 2 metals.
(a) Periodicity is the repeating trend in properties of elements across different periods in
the periodic table.
(i) Complete the table below with the electron configurations and blocks.
Group 2 Group 17 (7)
Period 2 Be F
1s2 ........................................................ 1s2 ........................................................
Period 3 Mg Cl
1s2 ........................................................ 1s2 ........................................................
Block
............................. .............................
(ii) Use your answers to (a)(i) to explain why electron configuration is an example of a
periodic trend.
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
............. [2]
(iii) Mg forms 2+ ions but Cl usually forms 1– ions in their reactions. Explain why.
© OCR 2024
*1327955883*
Tuesday 21 May 2025 – Morning
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 20 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2024 [601/5256/4] DC (PQ/SG) 334107/3
OCR is an exempt Charity
Turn over
1 This question is about water, H2O, and ammonia, NH3.
, 2
(a) Hydrogen and oxygen have different electronegativities.
What is meant by the term electronegativity?
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
............. [2]
(b) H2O is a polar molecule that has hydrogen bonding.
(i) Complete the diagram below to show hydrogen bonding between the H 2O molecule
shown and another H2O molecule.
Include relevant dipoles and lone pairs.
Label the hydrogen bond.
O
H H
(ii) Explain why molecules of H2O are polar.
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
............. [1]
(iii) One unusual property of H2O is that ice floats on water.
Explain why ice has a lower density than water.
........................................................................................................................................
..................
© OCR 2024
, 3
........................................................................................................................................
..................
........................................................................................................................................
............. [1]
(c) Solid ammonia, NH3, also contains hydrogen bonds.
(i) Suggest why solid ammonia has a lower melting point than ice.
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
............. [2]
(ii) When ammonia dissolves in water, ammonium ions, NH4+, are formed.
Draw a ‘dot-and-cross’ diagram to show the bonding in an NH4+ ion.
Show outer electrons only.
(iii) Outline how you would test for the presence of NH4+ ions in a solution.
Your answer should include observations.
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
............. [2]
© OCR 2024 Turn over
, 4
(d) A student heats 11.50 g of hydrated zinc sulfate, ZnSO 4•7H2O, to remove all the water
of crystallisation.
Calculate the mass of anhydrous zinc sulfate that should be obtained.
mass = ....................................................... g [3] 2 This question is about
periodicity and the reaction of some Group 2 metals.
(a) Periodicity is the repeating trend in properties of elements across different periods in
the periodic table.
(i) Complete the table below with the electron configurations and blocks.
Group 2 Group 17 (7)
Period 2 Be F
1s2 ........................................................ 1s2 ........................................................
Period 3 Mg Cl
1s2 ........................................................ 1s2 ........................................................
Block
............................. .............................
(ii) Use your answers to (a)(i) to explain why electron configuration is an example of a
periodic trend.
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
..................
........................................................................................................................................
............. [2]
(iii) Mg forms 2+ ions but Cl usually forms 1– ions in their reactions. Explain why.
© OCR 2024
