NJC 2022 H1 Chem Promo P1 Ans

NJC SH1 Promotional Examination 8873/01/2022 [Turn over 1 NATIONAL JUNIOR COLLEGE SH1 Promotional Examination Higher 1 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Optical Answer Sheet Data Booklet 8873/01 29 September 2022 40 mins 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 twenty 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: 2205648 25648 This document consists of 8 printed pages.

NJC SH1 Promotional Examination 8873/01/2022 2 Answer key for 2022 SH1 H1 Chemistry Promo Paper 1 1 C 11 D 2 B 12 B 3 D 13 A 4 B 14 D 5 A 15 A 6 B 16 C 7 D 17 A 8 C 18 C 9 D 19 C 10 C 20 A 1 How many hydrogen atoms are present in 4.0 g of methane? (L = Avogadro constant) A L 16 B L 4 C L D 4L Ans: C Amount of methane, CH4 = 4.0 16.0 = 0.25 mol Amount of H atoms in CH4 = 4 × 0.25 = 1 mol No. of H atoms = 1 × L = L 2 The table shows the relative abundance of a sample of naturally occurring isotopes of zinc. isotope relative abundance Zn30 64 10 Zn30 65 8 Zn30 67 2 Zn30 68 1 What is the relative atomic mass of this sample of zinc? A 64.0 B 64.9 C 68.1 D 72.2 Ans: B Ar = 64×10 + 65×8 +67×2+68×1 21 = 64.9

NJC SH1 Promotional Examination 8873/01/2022 [Turn over 3 3 Analysis of a mixture of two sulfur-containing gases show that H2S and CS2 are present in a 3 : 1 mole ratio. This mixture is burned in excess oxygen to give CO2 and SO2 gas. What is the mole ratio of the gases CO2 : SO2 obtained after complete combustion? A 1 : 2 B 1 : 3 C 1 : 4 D 1 : 5 Ans: D Let amount of H2S be 3x mol and CS2 be x mol, H2S + 3 2O2 → SO2 + H2O 3x 3x Amount of SO2 produced by H2S = 3x mol CS2 + 3O2 → 2SO2 + CO2 x 2x x Amount of SO2 produced