2024 Prelims ASRJC H2 Chem P1 (Ans)

ASRJC JC2 PRELIM 2024 9729/01/H2 [Turn over ANDERSON SERANGOON JUNIOR COLLEGE 2024 JC2 PRELIMINARY EXAMINATION NAME:______________________________ ( ) CLASS: 24 /____ CHEMISTRY 9729/01 Paper 1 Multiple Choice SUGGESTED SOLUTIONS 1 Use of the Data Booklet is relevant to this question. Which particle has more protons than electrons and more protons than neutrons? (D represents deuterium, 2H) A NH3 B NH3D+ C ND4+ D NHD− Ans: B Approach For a particle to contain more protons than electrons, it is likely to be a cation. Hence you should calculate the number of protons and neutrons for the particles in option B and C. NH3 NH3D+ ND4+ NHD− number of protons 7 + 3(1) = 10 7 + 3(1) + 1 = 11 7 + 4(1) = 11 7 + 1 + 1 = 9 number of neutrons 7 + 0 = 7 7 + 0 + 1 = 8 7 + 4(1) = 11 7 + 0 + 1 = 8 number of electrons 10 10 10 10 From the table above, NH 3D+ has 1 more proton than electron and 3 more protons than neutrons.

2 ASRJC JC2 PRELIM 2024 9729/01/H2 2 The graph shows the second ionisation energies of eight consecutive elements A to H, in Period 2 and 3 of the Periodic Table. [Note that letters A to H are not the atomic symbols of the elements concerned.] Which statements are correct? 1 F and G are in the same period in the Periodic Table. 2 The general increase from A to F is due to increasing atomic radius. 3 The small decrease from C to D is due to repulsion between paired electrons. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 3 only Ans: B Statement 1 is correct. The sharp dip in 2 nd IE from F to G suggest that the second electron in G is removed from an electron shell which is further away / more shielded from the nucleus. The second electron removed from F is from the inner quantum shell. F is in group 1. G is in Group 2. Statement 2 is incorrect. • IE is not affected by atomic radius. IE is affected by nuclear charge, shielding effect and the distance of the valence electron from the nucleus. • From A+ to F+, nuclear charge increases. Number of electron shells remains the same and shielding effect remains approximately constant. Electrostatic attraction between the valence electrons and the nucleus becomes stronger. More energy is required to remove a valence electron from an atom across a period. • Due to the stronger attraction between the valence electrons and nucleus, atomic radius also decreases. Statement 3 is correct. C+: 1s22s22p3 D+: 1s22s22p4 The 2p electron to be removed from D+ is a paired electron while that to be removed from C+ is an unpaired electron. Due to inter -electronic repulsion between paired electrons in the same orbital, less energy is required to remove the 3p electron from D+.

3 ASRJC JC2 PRELIM 2024 9729/01/H2 [Turn over 3 Tyrosine is an amino acid. In which sequence is the bond angles arranged in decreasing order? A x > y > z B y > z >