NJC_2025_H1_Chemistry_Prelim_P2_Ans

1 NJC/H1 Chem Preliminary Examination/02/2025 [Turn over NATIONAL JUNIOR COLLEGE SH2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 2 Structured Questions Candidates answer on the Question Paper. Additional Materials: Data Booklet 8873/02 16 September 2025 2 hours READ THESE INSTRUCTIONS FIRST Write your name, registration number and subject class on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, glue or correction fluid. The use of an approved scientific calculator is expected, where appropriate. Section A Answer all the questions. Section B Answer one question. At the end of the examination, fasten all your work securely together. A1 /13 A2 /13 Paper 2 /80 A3 /6 Paper 1 /30 A4 /11 Weightage A5 /10 Paper 1 (33%) /33 A6 /7 Paper 2 (67%) /67 B6 / B7 /20 Overall The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 23 printed pages and 1 blank page. Section A

2 NJC/H1 Chem Preliminary Examination/02/2025 Answer all the questions in this section in the spaces provided. 1 Boron, carbon, and lithium play critical roles in nuclear, organic, and battery chemistry. Their atomic structure and periodic behaviour provide important insights into chemical properties and bonding patterns. (a) (i) About 0.005% of water molecules consist of an oxygen atom bonded to two atoms of the isotope of hydrogen, deuterium, . The compound formed is deuterium oxide, D2O, and is also known as ‘heavy water’. Define the term isotope. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. [1] (ii) State the number of subatomic particles present in one molecule of D2O. number of protons number of neutrons number of electrons Protons: 10 (8 from O, 1 from each D)  Neutrons: 12 (8 from O, 2 from each D)  Electrons: 10 (8 from O, 1 from each D) [1] (b) Separate beams of 14C2– and 7Li+ ions are passed through an electric field in the set- up below. The angle of deflection of the 14C2– beam is 7.0 o. Sketch on the diagram below, the paths taken by beams of 7Li+ and 14C2– ions in the presence of an electric field. Label your sketch clearly.

3 NJC/H1 Chem Preliminary Examination/02/2025 [Turn over  1 mark: ¹⁴C²⁻ deflects toward positive plate, curved path labelled (angle = 7°)  1 mark: ⁷Li⁺ deflects toward negative plate, with greater curvature than ¹⁴C² ⁻ (Opposite directions, and lighter ion deflects more.) [2] (c) The element sulfur has four naturally occurring isotopes as shown in Table 1.2. Table 1.2 isotope relative abundance / % 32S 94.93 33S 0.76 34S 4.29 36S 0.02 Use the relat