Iodine is an element in Group 17 of the Periodic Table - CIE - A-Level Chemistry - Question 2 - 2019 - Paper 1
Question 2
Iodine is an element in Group 17 of the Periodic Table.
(a) (i) At room temperature, iodine solid has a lattice structure.
Describe the arrangement of the iodine mo... show full transcript
Worked Solution & Example Answer:Iodine is an element in Group 17 of the Periodic Table - CIE - A-Level Chemistry - Question 2 - 2019 - Paper 1
Step 1
Describe the arrangement of the iodine molecules within the solid.
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Answer
Iodine molecules in solid form are arranged in a regular and uniform lattice structure. This arrangement ensures that the molecules are held together tightly, providing stability to the solid.
Step 2
List all of the forces of attraction present in solid iodine and identify which of these are overcome when solid iodine is heated to produce iodine vapour.
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Answer
The forces of attraction present in solid iodine include covalent bonds as well as temporary (induced) dipoles. When solid iodine is heated to produce vapour, it is primarily the temporary (induced) dipoles that are overcome.
Step 3
How many co-ordinate (dative covalent) bonds are made when a molecule of AlI6 is formed from its atoms?
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Answer
In the formation of a molecule of AlI6, a total of 2 co-ordinate (dative covalent) bonds are made.
Step 4
Describe how co-ordinate (dative covalent) bonds form within this molecule.
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Answer
Co-ordinate (dative covalent) bonds in the AlI6 molecule form when iodine atoms donate a pair of electrons to the aluminum ion, creating a stable bond.
Step 5
Write an equation for this reaction.
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Answer
The balanced equation for the reaction between hydrogen iodide and concentrated sulfuric acid is:
2H2SO4+14HI→7I2+8H2O+H2S+S
Step 6
Explain, with reference to oxidation numbers, why this reaction is a redox reaction.
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Answer
This reaction is classified as a redox reaction because the oxidation number of iodine increases from -1 in hydrogen iodide to 0, indicating oxidation. Simultaneously, the oxidation number of sulfur decreases from +6 in sulfuric acid to +4, indicating reduction. Hence, there is a transfer of electrons within the reaction.
