2023 VJC H2 Chem Prelim P1 (Ans)

1 VICTORIA JUNIOR COLLEGE 2023 JC2 PRELIMINARY EXAMINATION H2 CHEMISTRY PAPER 1 ANSWERS 1 D 6 D 11 C 16 B 21 D 26 B 2 C 7 A 12 D 17 C 22 A 27 B 3 B 8 D 13 B 18 D 23 C 28 C 4 C 9 D 14 B 19 D 24 A 29 A 5 A 10 B 15 C 20 C 25 B 30 A 1 D No of protons No of e– No of neutrons A: Wrong For Al13 27 13 13 27 – 13 = 14 B: Wrong For Cl– 17 35 17 17 + 1 = 18 35 – 17 = 18 C: Wrong For S2–16 32 16 16 + 2 = 18 32 – 16 = 16 D: Correct For K+19 39 19 19 – 1 = 18 39 – 19 = 20 2 C Since central C atom is sp hybridised and there are no unpaired electrons, C2O molecule has the following structure: Hence, C2O has 3 lone pairs of electrons. 3 B (1 and 2 only) Option 1: Correct It shows the structure of diamond which has a giant molecular structure. Option 2: Correct It shows the structure of graphite which has a layered giant molecular structure. Option 3: Wrong Sodium chloride has a giant ionic structure. Option 4: Wrong Iodine has a simple molecule structure. The molecules are held by weak intermolecular forces of attraction. It has a solid lattice structure. 4 C PV = nRT PV = (m/Mr)RT Mr = mRT/(PV) Given the same mass of gases in the identical flasks of same volume, hence, m, V and R are constant, Mr ∝ T/P For gas E For gas F For gas G Mr ∝ t/p Mr ∝ t/2p Mr ∝ 2t/p Hence, Mr(G) > Mr(E) > Mr(F) 5 A Option A: Correct Real gases behave less ideally at high pressure. At high pressure, real gases behave less ideally as the gas particles are close to each other and size of the particle is not negligible. Option B: Wrong Real gases behave more ideally at high temperature. Intermolecular forces of attraction is negligible at high temperature since gas particles have sufficient kinetic energy to overcome it. Option C: Correct The presence of a catalyst increases the rates of both the forward and backward reactions. It does not have any effect on the ideal behaviour of gas. Option D: Wrong Strong covalent bonds between the nitrogen atoms does not explain if the gas is behaving ideally. We should consider the intermolecular attractions between the molecules instead. 6 D For element X: Chloride and oxide dissolve to give strong acidic solution  P or S For element Y: Low conductivity at room temperature  Si Only 1 chloride with formula SiCl4  Si Chloride dissolves giving acid solution  Si For element Z: Chloride and oxide have high m.p.  Na or Mg Oxide reacts readily in water  Na Chloride dissolves giving neutral solution  Na 7 A Down Group 2, charge density of cation ( ∝ q+/r+) decreases, causing the polarising power of cation to decrease. As a result, there is less distortion (or polarisation) of the anionic charge cloud and so the iodate becomes more stable to heat down the group. This means that iodate is decomposed at a higher temperature. With the mass of Q( IO3)2 being unchanged with time upo