2023 TMJC H2 Chem Prelim P2 (QP)

2023 H2 Chem Prelim P2 (QP) 1 The Periodic Table shows many interesting and recurring trends. (a) The variation of 1st ionisation energies across Period 4 is similar to that of Period 3. Table 1.1 shows the 1st ionisation energies of six consecutive elements in Period 4. Table 1.1 element Ga Ge As Se Br Kr 1st ionisation energy / kJ mol–1 580 760 950 1140 1350 (i) Explain why the 1 st ionisation energies show a general increase from gallium to krypton. ................................ ................................ ................................ ............................ ................................ ................................ ................................ ............................ ................................ ................................ ................................ ............................ ................................ ................................ ................................ ............................ ................................ ................................ ................................ ............................ ................................ ................................ ................................ ............................ ................................ ................................ ................................ ....................... [2] (ii) Using your knowledge of the variations, c omplete Table 1.1 with a suggested value for the first ionisation of selenium. [1] (b) Electrical conductivity is measured in Siemens per meter, S m –1, where a higher value represents higher electrical conductivity. Calcium is a Group 2 metal and has an electrical conductivity of 2.9 × 107 S m–1 while copper is a transition metal and electrical conductivity of 5.9 × 107 S m–1. (i) State the full electronic configuration of copper. ................................ ................................ ................................ ....................... [1] (ii) Explain the difference in electrical conductivity between calcium and copper. ................................ ................................ ................................ ............................ ................................ ................................ ................................ ............................ ................................ ................................ ................................ ............................ ................................ ................................ ................................ ....................... [2]

2 2023 H2 Chem Prelim P2 (QP) Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry (c) Other transition metals such as nickel and platinum are sometimes found in copper ores. To obtain pure copper, the ore was made the anode of an electrolysis cell, with a pure copper cathode and aqueous CuSO4 as electrolyte. Explain, with refer