VJC 2022 H2 Chem Prelim P1_ans_

1 Victoria Junior College 2022 H2 Chemistry Prelim Exam 9729/1 Suggested Answers 1 B 2 D 3 B 4 A 5 A 6 D 7 C 8 A 9 C 10 D 11 B 12 C 13 A 14 B 15 B 16 C 17 C 18 B 19 B 20 D 21 A 22 A 23 C 24 C 25 D 26 D 27 D 28 C 29 C 30 B 1 B element electronic configuration no. of unpaired e− A Al 1s22s22p63s23p1 1 O 1s22s22p4 2 B B 1s22s22p1 1 H 1s1 1 C Cu [Ar]3d104s1 1 I [Kr]4d105s25p5 1 D Fe [Ar]3d64s2 4 Cl 1s22s22p63s23p5 1 2 D Large dip in second I.E. from M to N → second electron removed from an outer shell in N → M is in Group 1 (Na) while N is in Group 2 (Mg). Option A: True L is a noble gas (Ne). It has a fully filled valence electron shell and does not form an oxide. Option B: True Q is silicon (Si) which has the highest melting point across period 3. Si has a giant molecular structure. Large amount of energy is required to break the strong covalent bonds. Option C: True The atomic radius of J (O) is larger than that of K (F). Both O and F are in the same period (similar shielding effect), but F has a greater number of protons (higher nuclear charge), hence higher effective nuclear charge, and valence electrons are pulled closer to the nucleus. So F has a smaller atomic radius than O. Option D: False The oxide of N (MgO) has a higher melting point than the oxide of R (P4O10). 3 B molecule no. of bp no. of lp shape bond angle A SO2 2 1 bent 118° OF2 2 2 bent 105° B OCS 2 0 linear 180° HCN 2 0 linear 180° C CCl4 4 0 tetrahe dral 109.5° XeF4 4 2 square planar 90° D CS2 2 0 linear 180° H2S 2 2 bent 105° 4 A Statement 1: Correct In all the three allotropes, each carbon atom is covalently bonded to 3 other carbon atoms. The remaining electron is delocalised and mobile. The p orbitals of the carbon atoms overlap to form a continuous π electron cloud allowing delocalisation of electrons and conduction of electricity. Statement 2: Incorrect Unlike graphite, graphene and carbon nanotube do not have layers held together by weak intermolecular forces of attraction . Hence they are not slippery to be used as lubricants. Statement 3: Incorrect Note that both carbon allotropes are non −polar. Energy released from the formation of dipole−induced dipole interactions between carbon allotropes and water is insufficient to overcome the strong C-C covalent bonds in the carbon nanotube and graph ene as well as the hydrogen bonds between water molecules. 5 A Since GA has a higher Mr than GB, and mass of the two gases is the same, amount of G A is lower than amount of GB. For an ideal gas, pV = nRT. Option A: Correct At constant p, 𝑉 = 𝑛𝑅 𝑝 𝑇 . Plotting V against T gives a straight line graph passing through the origin with constant gradient 𝑛𝑅 𝑝 . Option B: Incorrect At constant T, pV = nRT = constant. Plotting pV against V gives a horizontal line. Option C: Incorrect At constant T, pV = nRT = constant. Plotting p against pV giv