A-LevelChemistryChemical bonding9701/23 · May/June 2019 · Q29 Marks

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 molecules within the solid. [1] (ii) 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. force(s) of attraction present force(s) of attraction overcome [2] Iodine reacts with aluminium to form a white solid, Al2I6. (b) The diagram shows the arrangement of the outer electrons within a molecule of Al2I6. [Figure 2.1 showing a molecule of Al2I6 with iodide and aluminium atoms and XX representing shared electron pairs] (i) How many co-ordinate (dative covalent) bonds are made when a molecule of Al2I6 is formed from its atoms? [1] (ii) Describe how co-ordinate (dative covalent) bonds form within this molecule. [1] (c) In a reaction between hydrogen iodide and concentrated sulfuric acid, the products are hydrogen sulfide, sulfur, iodine and water. (i) Write an equation for this reaction. You may wish to use oxidation numbers to help you. [2] (ii) Explain, with reference to oxidation numbers, why this reaction is a redox reaction. [2] [Total: 9]

(a)(i)At room temperature, iodine solid has a lattice structure. Describe the arrangement of the iodine molecules within the solid.[1]
(a)(ii)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. force(s) of attraction present force(s) of attraction overcome[2]
(b)(i)How many co-ordinate (dative covalent) bonds are made when a molecule of Al2I6 is formed from its atoms?[1]
(b)(ii)Describe how co-ordinate (dative covalent) bonds form within this molecule.[1]
(c)(i)Write an equation for this reaction. You may wish to use oxidation numbers to help you.[2]
(c)(ii)Explain, with reference to oxidation numbers, why this reaction is a redox reaction.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

[1] held in regular / uniform arrangement
[2] M1 covalent (bonds) AND (temporary) induced dipoles
[2] M2 (temporary) induced dipoles
[1] 2
[1] iodine (atom/s) donates a pair of electrons (to the Al-I covalent bond / s).
[2] M1 correct species
[2] M2 correctly balanced equation
[2] M1 I (oxidation number increases) from –1 to 0 = oxidation / reducing agent
[2] M2 S (oxidation number decreases) from (+) 6 to 0 OR -2 = reduction / oxidising agent

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.