2025 JC2 Prelims H1 Chem Paper 2 Solutions_TJC

8873 / TJC Prelims / 2025 DO NOT WRITE IN THIS MARGIN 2025 TJC H1 Chemistry Prelim Paper 2 Worked Solutions Section A 1 (a) (i) [1] W. It has the highest q r + + value Note : C is not a metallic element (ii) [1] V or Cr (iii) [✓] Giant metallic structure with strong [✓] electrostatic forces of attraction between cations and sea of delocalised electrons. [1] 2[✓] = 1m (iv) [1] Adding carbon atoms into the space between the iron atoms in the lattice will prevent the iron atoms from sliding over each other easily and hence do not go out of shape easily. (b) FeCl2 has a [✓] giant ionic structure while [✓] SiCl4 and SiI4 have simple molecular structures. Between Fe2+ and Cl- ions, there are [✓] strong ionic bonds while between SiCl 4 molecules and between SiI 4 molecules, there are [✓] weak instantaneous dipole -induced dipole attractions (id-id). Hence [✓] more energy is required to overcome the strong ionic bonds than the weak id-id attractions resulting in a high m.p. for FeCl2. SiI4 has a [✓] bigger electron cloud compared to SiCl 4 resulting in [✓] greater polarization leading to [✓] stronger id -id attractions between SiI 4 molecules. Hence [✓] more energy required to overcome the id-id attractions resulting in higher m.p. for SiI4. 3[✓] = [1]

3 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 8873 / TJC Prelims / 2025 DO NOT WRITE IN THIS MARGIN [Turn over 2 (a) [1] The product of reduction of H 2O2 is water/oxygen which is clean / non-pollutants / environmentally friendly. Note: accept O2 (b) [✓] Sufficient energy is released from the formation of [✓] hydrogen bonds between water and H2O2 to overcome the [✓] hydrogen bonds between water molecules and hydrogen bonds between H2O2 molecules. [✓] Insufficient energy is released from the formation of [✓] instantaneous dipole - induced dipole interactions between anthraquinone and water to overcome the hydrogen bonds between water molecules. [✓] H2O2 dissolve in water / anthraquinone cannot dissolve in water. 3[✓] = [1] (c) (i) [1] Palladium catalyst is not in the same phase as the reactants. (ii) The reactant molecules are [✓] adsorbed unto the surface of the solid catalyst. This [✓] lowers the activation energy by [✓] increasing the surface concentration of reactant molecules (or: reactant molecules are brought closer together) and [✓] weakens the covalent bonds of/within the reactant molecules. [✓] Number of particles with energy greater than or equal to Ea’ increases. The [✓] frequency of effective collisions is increased. [✓] Rate constant increases and hence the rate of the reaction increases. After the reaction, [✓] desorption of product molecules occur at the catalyst surface. The product molecules eventually [✓] break free and diffuse away from the catalyst surface. Other reactant molecules may then approach the catalyst surface. 3[✓] = [1] ; Diagram = [1]