2024 TMJC H2 Chem Prelim P1 (Ans)

___________________________________________________________________ H2 CHEMISTRY 9729/01 Paper 1 Multiple Choice 19 September 2024 1 hour Additional materials: Multiple Choice Answer Sheet Data Booklet _________________________________________________________________________ READ THESE INSTRUCTIONS FIRST Write in soft pencil. Write your name, class and register number on the Answer Sheet in the spaces provided. There are thirty questions in 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 use of the Answer Sheet very carefully. You are advised to fill in the Answer Sheet as you go along . No additional time will be given for the transfer of answers once the examination has ended. 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 14 printed pages. Use of the Answer Sheet Ensure you have written your name, class register number and class on the Answer Sheet. Use a 2B pencil to shade your answers on the Answer Sheet; erase any mistakes cleanly. Multiple shaded answers to a question will not be accepted. For shading of class register number on the Answer Sheet, please follow the given examples: If your register number is 1, then shade 01 in the index number column. If your register number is 21, then shade 21 in the index number column. TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION

2 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H2 Chemistry 1 Use of the Data Booklet is relevant to this question. A stream of gaseous Ca2+ 20 40 charged ions was passed through an electric field between two oppositely charged plates and the Ca2+ ions were deflected at an angle of +15.0°. Under the same electric field, a stream of unknown gaseous X3− ion was deflected at an angle of −29.0°. What is a possible atomic number of X? A 15 B 24 C 31 D 34 Answer: A angle of deflection q m ratio q m of Ca2+ 20 40 = 2 40 ➔ +15.0° q m of X3− = 3 Ar of X ➔ −29.0° 29 15 = 3 𝐴𝑟 𝑜𝑓 𝑋 2 40 Ar, mass of X = 31. 0 X could be phosphorus with 15 protons and 16 neutrons 2 Which statements correctly describe an electron shell with the principal quantum shell number n = 2? 1 A total of 10 electrons can be accommodated in this shell. 2 An orbital from this shell must be dumb-bell in shape. 3 The energy level of the orbitals in this shell is higher than that in n = 1. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 3 only Answer: D Only 3 is correct An orbital in this shell may either be spherical or dumb−bell in shape. A total of 8 electrons can be accommodated in this shell. 

3 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H2 Chemistry [Turn over 3 The table identifies the shape and polarity of four molecules. Which row is correct? molecule molecular shape polarity A bromine trifluoride bent polar B phosphorus trichloride trigonal pyramidal polar C sulfur dichloride linear non-polar D trifluoromethane tetrahedral non-polar Answer: B 4 The table shows four species with their corresponding physical properties. Which species does not correspond to its description of physical properties? species physical properties A copper high melting point, conducts electricity when solid and when molten B silicon dioxide high melting point, does not conduct electricity in any state C aluminium bromide high melting point, conducts electricity when molten but not when solid D phosphorus pentachloride low melting point, does not conduct electricity in any state Answer: C species structure A Cu giant metallic B SiO2 giant molecular C AlBr3 simple molecular, not giant ionic, does not conduct electricity in any state D PCl5 simple molecular BrF3 3 bp 2 lp T-shaped polar PCl3 3 bp 1 lp trigonal pyramidal polar SCl2 2 bp 2 lp bent polar CHF3 4 bp 0 lp tetrahedral polar

4 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H2 Chemistry 5 Use of the Data Booklet is relevant to this question. Which of the following shows the correct trends when the melting points of the elements, Mg, Al, Si and P are plotted against their atomic radii? Answer: A Across the period, from Mg to P,  Atomic radius decreases.  Atomic radii: Mg > Al > Si > P (Option C is wrong.) Across the period,  Si has the highest melting point. (Option B is wrong.)  Al has a higher melting point than Mg due to stronger metallic bonds. (Option D is wrong.) 6 Which statement is correct about the halogens (X2) chlorine, bromine and iodine as well as their corresponding hydrogen halides (HX)? A The colour intensity of the halogens decreases from Cl2 to I2. B The oxidising power of the halogens decreases from Cl2 to I2. C The thermal stability of HX increases from HCl to HI. D The volatility of HX increases from HCl to HI. Answer: B The oxidising power of the halogens decreases down the group from chlorine to iodine. A B C D

5 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H2 Chemistry [Turn over 7 Which graph correctly represents the relationship between ( 1 pV) and pressure for an ideal gas at constant temperature? Answer: A Rearranging the ideal gas equation pV = nRT, 1 pV= 1 nRT = k Graph is straight line graph with gradient = 0 (horizontal line) 8 1 dm3 of a gaseous hydrocarbon was mixed with excess oxygen. When the mixture undergoes complete combustion, the volume contracted by 2 dm3. When the resultant mixture was passed through concentrated sodium hydroxide, the gas volume further decreased by 2 dm3. All volumes were measured at room temperature and pressure. What is the empirical formula of the hydrocarbon? A CH B CH2 C C2H3 D C3H4 Answer: B Since gaseous volume ∝ amounts, put in the coefficients, deducing: 1 CxHy(g)+ 3 O2(g)→ 2 CO2(g) + ? H2O(l) Balancing C atoms, we get x = 2 Balancing O atoms, we find coefficient of H2O is 2, hence y = 4 Hence, hydrocarbon is C2H4 and empirical formula is CH2. 1 pV p 1 pV p 1 pV p 1 pV p A B C D

6 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H2 Chemistry 9 Substances X and Y react to form product Z. 2X + Y → 2Z The reaction was studied and the following data were obtained. experiment [X] / mol dm−3 [Y] / mol dm−3 initial rate / mol dm−3 min−1 1 0.10 0.10 0.020 2 0.20 0.10 0.080 3 0.15 0.23 0.045 What is the order of reaction with respect to X and Y? A First order with respect to X and zero order with respect to Y. B Second order with respect to X and first order with respect to Y. C First order with respect to X and first order with respect to Y. D Second order with respect to X and zero order with respect to Y. Answer: D Compare experiments 1 and 2 to determine the order with respect to X: [X] changes from 0.10 to 0.20 (doubles), [Y] is constant. Initial rate changes from 0.020 to 0.080 (quadruples)  2nd order wrt X Compare experiments 1 and 3 to determine the order with respect to Y: [X] changes from 0.10 to 0.15 (× 1.5), and