Tuesday 21 May 2024 – Morning
AS Level Chemistry A
H032/02 Depth in chemistry
Time allowed: 1 hour 30 minutes
Turn over
, 2
1 This question is about water, H2O, and ammonia, NH3.
(a) Hydrogen and oxygen have different electronegativities.
What is meant by the term electronegativity?
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(b) H2O is a polar molecule that has hydrogen bonding.
(i) Complete the diagram below to show hydrogen bonding between the H2O molecule shown and
another H2O molecule.
Include relevant dipoles and lone pairs.
Label the hydrogen bond.
O
H H
[2]
(ii) Explain why molecules of H2O are polar.
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(iii) One unusual property of H2O is that ice floats on water.
Explain why ice has a lower density than water.
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© OCR 2024
, 3
(c) Solid ammonia, NH3, also contains hydrogen bonds.
(i) Suggest why solid ammonia has a lower melting point than ice.
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(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.
[2]
(iii) Outline how you would test for the presence of NH4+ ions in a solution.
Your answer should include observations.
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(d) A student heats 11.50 g of hydrated zinc sulfate, ZnSO4•7H2O, to remove all the water of
crystallisation.
Calculate the mass of anhydrous zinc sulfate that should be obtained.
mass = ....................................................... g [3]
© OCR 2024 Turn over
, 4
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
............................. .............................
[3]
(ii) Use your answers to (a)(i) to explain why electron configuration is an example of a periodic trend.
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..................................................................................................................................................... [2]
(iii) Mg forms 2+ ions but Cl usually forms 1– ions in their reactions. Explain why.
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..................................................................................................................................................... [2]
(iv) Magnesium reacts with oxygen in the air.
Write the equation for this reaction.
..................................................................................................................................................... [1]
© OCR 2024
AS Level Chemistry A
H032/02 Depth in chemistry
Time allowed: 1 hour 30 minutes
Turn over
, 2
1 This question is about water, H2O, and ammonia, NH3.
(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 H2O molecule shown and
another H2O molecule.
Include relevant dipoles and lone pairs.
Label the hydrogen bond.
O
H H
[2]
(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.
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... [1]
© OCR 2024
, 3
(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.
[2]
(iii) Outline how you would test for the presence of NH4+ ions in a solution.
Your answer should include observations.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... [2]
(d) A student heats 11.50 g of hydrated zinc sulfate, ZnSO4•7H2O, to remove all the water of
crystallisation.
Calculate the mass of anhydrous zinc sulfate that should be obtained.
mass = ....................................................... g [3]
© OCR 2024 Turn over
, 4
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
............................. .............................
[3]
(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.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... [2]
(iv) Magnesium reacts with oxygen in the air.
Write the equation for this reaction.
..................................................................................................................................................... [1]
© OCR 2024
