NJC_2024_H1_Chem_Prelim_P1_Ans

NJC/H1 Chem Preliminary Examination/01/2024 [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 19 September 2024 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 15 printed pages and 1 blank page.

2 NJC/H1 Chem Preliminary Examination/01/2024 Suggestion solution for P1 (MCQ) 1 C 11 C 21 D 2 B 12 A 22 C 3 C 13 C 23 B 4 B 14 B 24 A 5 A 15 D 25 B 6 D 16 C 26 A 7 B 17 C 27 A 8 A 18 C 28 D 9 A 19 D 29 B 10 B 20 A 30 D

3 NJC/H1 Chem Preliminary Examination/01/2024 [Turn over 1 Use of the Data Booklet is relevant to this question. A sample of 35.6 g of hydrated sodium carbonate contains 25.84% sodium ions by mass. When this sample is heated, anhydrous sodium carbonate and water vapour are formed. What is the mass lost? A 7.2 g B 10.6 g C 14.4 g D 21.2 g Ans: C Na2CO3.xH2O → Na2CO3 + xH2O 46 106 + 18(𝑥) × 100% = 25.84 x = 4 Mass of water given off = 35.6 178 × 18 × 4 = 14.4g 2 Diamond is an allotrope of carbon. The mass of a diamond can be measured in carats. One carat is 0.200 g of carbon. Which expression gives the number of carats that contain 6.02 × 1023 carbon atoms? A 0.200 × 12.0 B 12.0 0.200 C 0.200 12.0 D 0.200 6.02 × 1023 × 12.0 Ans : B 1 mol of C contains 6.02 × 1023 C atoms Mass of C = 12.0 g Number of carat = 12.0 0.200

4 NJC/H1 Chem Preliminary Examination/01/2024 3 One of the main chemicals in air bags in cars is the ionic compound sodium azide, NaN3. When the car is in a violent head-on impact, a sensor causes ignition of the sodium azide to form nitrogen gas explosively, rapidly filling the air bag. I 2NaN3 → 2Na + 3N2 Fine particles of potassium nitrate and silicon dioxide are al