2024 TMJC H1 Chem Prelim P1 (Ans)

___________________________________________________________________ H1 CHEMISTRY 8873/01 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 section. Answer all questions. For each question, there are four possible answers labelled A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read very carefully the instructions on the use of Answer Sheet. 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. This document consists of 13 printed pages and 1 blank page. Use of 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 H1 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 of these statements correctly describes 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 Use of the Data Booklet is relevant to this question. The first ionisation energy of beryllium is greater than the first ionisation energy of boron. Which factor explains this? A charge on the nucleus B distance from the nucleus to the outer electrons C removal of electron is from a lower energy orbital D repulsion between electrons in an orbital 

3 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H1 Chemistry Answer: C Be: Be(g) ⎯→ Be+(g) + e– 1st IE = +900 kJ mol–1 1s2 2s2 2p6 3s2 1s2 2s2 2p6 3s1 B: B(g) ⎯→ B+(g) + e– 1st IE = +799 kJ mol–1 1s2 2s2 2p6 3s2 3p1 1s2 2s2 2p6 3s2 Option A is incorrect as going from Be to B, nuclear charge increases, which should account for Be having a lower (not greater) 1st IE than B. Option B is incorrect as Be is (atomic radius: 0.112 nm) expected to be larger than B (atomic radius 0.080 nm), and less energy required if this was the case. Option C is correct as the electron in Be is removed from the s orbital which is lower in energy than the p orbital for B, hence more energy required for 1st IE. Option D is incorrect due to inter-electron repulsion would result in lower 1st IE for Be than B if this was the case. 4 Which of the following does not contain hydrogen bonding? A NH3(l) B NH4Cl(l) C (CH3)2NH(l) D CH3CONH2(l) Answer: B NH4Cl(l) contains ionic bonding instead of hydrogen bonding. The rest of the structures contain hydrogen bonding. 5 The CO2 molecule is linear. What is the number of  and  bonds present in the molecule?   A 1 3 B 2 2 C 3 1 D 4 0 Answer: B Each C=O bond in O=C=O comprises of 1  and 1  bonds, hence 2  and 2  present.

4 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H1 Chemistry 6 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 7 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 molecule No of bond pairs (bp) and lone pairs (lp) molecular shape polarity 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

5 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H1 Chemistry 8 Which of the following is not an acid−conjugate base pair? A HCl and NaCl B Na2HPO4 and H3PO4 C H2O2 and HO2− D CH3CH2NH2 and CH3CH2NH3Cl Answer: B Acid-conjugate base pair differs by 1 H+, but HPO42– and H3PO4 differs by 2 H+. 9 Which one of the following acid solutions can be used to give an effective buffer solution by partial neutralisation with aqueous NaOH? A HCOOH B HCl C HI D HNO3 Answer: A For an effective acidic buffer, there should be a weak acid and its conjugate base. HCOOH is a weak acid; when partially neutralised, the HCOO– conjugate base will be present together with HCOOH, giving rise to the buffer. The other acids are strong acids.

6 Tampines Meridian Junior College 2024 JC2 Preliminary Examination H1 Chemistry 10 The graph shown can be plotted for the titration of aqueous ethanoic acid with potassium hydroxide. Which species are present in the solution at point X? 1 ethanoic acid 2 potassium hydroxide 3 potassium ethanoate A 1 and 2 only B 1 and 3 only C 2 and 3 only D 3 only Answer: D Region X is a (basic) salt solution of potassium ethanoate where all the ethanoic acid has been completely neutralised. 11 Which pair of statements is correct for Group 1 elements and their reducing strength? reducing strength reason A decreases down the Group valence electron more easily lost B decreases down the Group valence electron more easily gained C increases down the Group valence electron more easily lost D increases down the Group valence electron more easily gained Answer: C Down Group 1, nuclear charge increases while number of electron shells and shielding effect increases. Hen