ACJC 2022 Prelim P2 QP

3 © ACJC 2022 9729/02/Prelim/2022 [Turn over Answer all the questions in the spaces provided. 1 (a) Table 1.1 shows the solubility of two organic molecules at 25 °C. Table 1.1 solubility in water / g dm–3 propanone miscible chloromethane 5.04 (i) Identify the type of intermolecular force present between the molecules. propanone: …………………………………………………………………........ chloromethane: ……………………………………………………………….[1] (ii) Give a reason for the difference in their solubilities in water. ………………………………………………………………………………...….. ………………………………………………………………………………….[1] (b) The boiling point of three ligands are shown in Table 1.2. Table 1.2 ligand formula boiling point / °C water H2O 100 ammonia NH3 –33.3 hydrazine N2H4 114 (i) Explain what is meant by the term ligand. ………………………………………………………………………………...….. ………………………………………………………………………………….[1] (ii) Explain the difference in the boiling points of the three ligands. ………………………………………………………………………………...….. ………………………………………………………………………………...….. ………………………………………………………………………………...….. ………………………………………………………………………………...….. ………………………………………………………………………………….[2]

4 © ACJC 2022 9729/02/Prelim/2022 [Turn over (c) Polydentate ligands are ligands which form more than one bond with the metal atom or ion. Salicylaldehyde, ethane-1,2-diamine and H2salen are examples of such ligands. H2salen can be synthesised from salicylaldehyde and ethane-1,2-diamine. When the phenolic groups of H 2salen are deprotonated, salen 2– acts as a ligand. It has a high affinity for Co2+ ions and forms a planar complex Co(salen). (i) Suggest the identity of molecule X. ………………………………………………………………………………….[1] (ii) Draw the structure of a salen2– ligand and circle the atoms which are used to coordinate to a Co2+ ion. salen2– [2] (iii) State the coordination number of the Co2+ ion in Co(salen). ………………………………………………………………………………….[1] (d) Ozonolysis is a method to oxidatively cleave alkenes using ozone, O3, to form carbonyl compounds.

5 © ACJC 2022 9729/02/Prelim/2022 [Turn over (i) 2-methyl-3-ethylpent-2-ene Draw the structure of the organic products when 2-methyl-3-ethylpent-2-ene undergoes ozonolysis. [2] (ii) Ozonolysis of A,C6H10, gives a single compound, B,C6H10O2. B gives a yellow precipitate when treated with alkaline aqueous iodine and forms a red-brown precipitate when treated with Fehling’s solution. Draw the structures of the compounds A and B. [2] [Total: 13] AA A B

6 © ACJC 2022 9729/02/Prelim/2022 [Turn over 2 Chromium is a transition metal that is valued for its