2024 Prelims YIJC H2 Chem P1 (Ans)

©YIJC [Turn over YISHUN INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUGGESTED SOLUTIONS CG INDEX NO CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 9729/01 13 September 2024 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid/tape. Write your name and class 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. This document consists of 15 printed pages and 1 blank page.

©YIJC [Turn over 2 1 A sample of calcium contains three naturally occurring isotopes, 40Ca, 42Ca and 44Ca. The sample is made up of 96.64% of 40Ca and the relative atomic mass of calcium in this sample is 40.11. What is the percentage of the isotope 42Ca in the sample? A 0.44% B 0.67% C 1.22% D 2.09% Answer: C 40Ca 96.64% 42Ca x% 44Ca (3.36 – x)% 40.11 = (40.0 × 96.64) + (42.0x) + [(3.36 − x) × 44.0] 100 x = 1.22% 2 Aluminium chloride dimerises to give Al2Cl6. Which statement about aluminium chloride and its dimer is correct? A AlCl3 has a high melting and boiling point due to strong electrostatic forces of attraction between Al3+ and Cl−. B Each aluminium atom is surrounded by four chlorine atoms in the dimer, Al2Cl6. C Some of the bond angles decrease while some remains the same when AlCl3 dimerises to form Al2Cl6. D The geometry around each aluminium atom in Al2Cl6 is trigonal planar. Answer: B A: Aluminium chloride has simple molecular structure due to the high polarising powe of A l3+ and the polarisability of the Cl− ions. B: From the above diagram, each aluminium atom is surrounded by 4 chlorine atoms. C and D: As seen in the diagram, the bond angles will all decrease when aluminium chloride dimerises as the shape around the central aluminium atom changes from trigonal planar (120°) to tetrahedral (approximately 109.5°.) Al Cl Cl Cl xx xxxx xx xx xx xxxx xx + Al Cl Cl Cl xx xxxx xx xx xx xxxx xx Al Cl Cl Cl Al ClCl Clxx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx

©YIJC [Turn over 3 3 The graph shows the behaviour of one mole of an ideal gas. Which of the following