NJC_2025_H1_Chemistry_Prelim_P1_Ans

NJC/H1 Chem Preliminary Examination/01/2025 [Turn over NATIONAL JUNIOR COLLEGE SH2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Optical Answer Sheet Data Booklet 8873/01 23 September 2025 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid. Write your name, subject class and registration number on the Answer Sheet in the spaces provided unless this has been done for you. There are thirty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read the instructions on the Answer Sheet very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. The use of an approved scientific calculator is expected, where appropriate. Instructions on how to fill in the Optical Mark Sheet Shade the index number in a 5 digit format on the optical mark sheet: 2nd digit and the last 4 digits of the Registration Number. Example: Student Examples of Registration No. Shade: 2305648 35648 This document consists of 11 printed pages and 1 blank page.

2 NJC/H1 Chem Preliminary Examination/01/2025 Suggestion solution for P1 (MCQ) 1 A 11 C 21 B 2 D 12 D 22 B 3 C 13 C 23 B 4 C 14 D 24 D 5 B 15 A 25 B 6 C 16 B 26 C 7 C 17 C 27 D 8 A 18 D 28 B 9 D 19 D 29 B 10 B 20 C 30 C

3 NJC/H1 Chem Preliminary Examination/01/2025 [Turn over 1  decay occurs when an atom’s nucleus emits an alpha particle, which is a helium nucleus. The radioactive isotope, Radium 226, undergoes  decay. 88226𝑅𝑎 → 24𝐻𝑒 + X Which row in the table correctly describes the nuclear make-up of X? number of protons number of neutrons A 86 136 B 88 136 C 86 138 D 88 138 Ans: A No. of neutrons of Ra = 226 – 88 = 138 No of protons of X = 88 – 2 = 86 No. of neutrons of X = 138 – 2 = 136 2 Which of the elements have the most number of unpaired electrons? A F B O C Al D P Ans: D Electronic Configurations F: 1s2 2s2 2p5 O: 1s2 2s2 2p4 Al: 1s2 2s2 2p6 3s2 3p1 P: 1s2 2s2 2p6 3s2 3p3

4 NJC/H1 Chem Preliminary Examination/01/2025 3 The successive ionisation energies of element A and B are shown below. ionisation energies / kJ mol‒1 1st 2nd 3rd 4th 5th 6th 7th 8th A 1011 1907 2914 4964 6274 21267 25431 29872 B 1251 2298 3822 5159 6542 9362 11018 33604 What is the formula of the compound formed when A reacts with B? A AB B A2B C AB3 D AB4 Ans: C For A, the largest increase in I.E is from the 5th to 6th I.E => Group 15 For B, the largest increase in I.E is from the 7th to 8th I.E=> G