TMJC_2025_H2 Chem_P2_Answer

CANDIDATE NAME CIVICS GROUP H2 CHEMISTRY 9729/02 Paper 2 Structured Questions 18 September 2025 2 hours Candidates answer on the Question Paper. Additional materials: Data Booklet This document consists of 24 printed pages. READ THESE INSTRUCTIONS FIRST Write your name and civics group in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams and graphs. Do not use paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part question. TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION For Examiner’s Use Percentage Paper 1 / 30 / 15 Paper 2 1 / 7 2 / 16 3 / 11 4 / 12 5 / 16 6 / 13 Paper 2 Total / 75 / 30 Paper 3 / 80 / 35 Paper 4 / 55 / 20 Grand Total / 100

2 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H2 Chemistry 1(a) The graph in Fig. 1.1 shows the atomic radii of some Period 4 metals. Fig. 1.1 (i) With reference to Fig 1.1, explain briefly why the atomic radius of Ca is smaller than K. [1] (ii) With reference to Fig 1.1, describe and explain why the atomic radii from Cr to Ni are relatively constant. [2] 0 50 100 150 200 250 K Ca Sc Ti V Cr Mn Fe Co Ni atomic radii/ pm Elements From Cr to Ni, • Nuclear charge increases. • Electrons are added to the inner 3d orbitals and provide shielding for the 4s / valence electrons. • Effective nuclear charge varies slightly OR Increase in nuclear charge is offset by the increase in shielding effect. Atomic radius remains relatively invariant/ relatively constant. Ca has greater nuclear charge than K while shielding effect remains relatively constant. Hence, Ca has a stronger electrostatic forces of attraction between nucleus and valance electrons than K, and the valence electrons of Ca are closer to the nucleus.

3 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H2 Chemistry (b) (i) Shibuichi is an alloy of copper and silver and is used in traditional Japanese sword fittings. A particular sample of Shibuichi produced the following peaks in its mass spectrum as shown in Fig 1.2. Fig. 1.2 Calculate the average Ar of copper from these data. [1] (ii) With reference to Fig. 1.2, state the number of protons and neutrons present in the atom with nucleon number 109. Number of protons: ___________ Number of neutrons: ___________ [1] 61.7 26.3 6.2 5.8