2023 ASRJC H2 Chem Prelim P1 MS

ASRJC JC2 PRELIMS 2023 9729/01/H2 [Turn over ANDERSON SERANGOON JUNIOR COLLEGE 2023 JC2 PRELIMINARY EXAMINATION WORKED SOLUTION NAME:______________________________ ( ) CLASS: 23 /____ CHEMISTRY 9729/01 Paper 1 Multiple Choice 21 September 2023 1 hour Additional Materials: Multiple Choice Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Write in soft pencil Do not use staples, paper clips, glue or correction fluid. Write your name, class and register number on the Answer Sheet. 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. Multiple Choice Answer Sheet Write your name, class and NRIC / FIN number, including the reference letter. Shade the NRIC / FIN number. Exam Title: JC2 PRELIM Exam Details: H2 Chemistry / Paper 1 Date: 21/09/2023

2 ASRJC JC2 PRELIMS 2023 9729/01/H2 1 In which species are the number of protons, neutrons and electrons all different? A 27 13 Al B 35 17 Cl – C 32 16 S2– D 39 19 K+ Ans D Work out the number for each of the options as follow. species 27 13 Al 35 17 Cl – 32 16 S2– 39 19 K+ no. of protons 13 17 16 19 no. of electrons 13 18 18 18 no. of neutrons 14 18 16 20 2 The ionisation energies, IE, of five elements are given in the table. second IE /kJ mol-1 third IE /kJ mol-1 fourth IE /kJ mol-1 B F Na Mg Al 2420 3370 4560 1450 1820 3660 6040 6940 7740 2740 25000 8410 9540 10500 11600 Which statement is correct? A The 2nd IE of F is higher than the 3 rd IE of Al because Al2+ has a higher nuclear charge than F+. B The 2nd IE of Mg is lower than 2 nd IE of Na because there is inter -electronic repulsion between the paired electrons in Mg+. C The 4th IE of B is higher than the 4th IE of Al because the electron to be removed from Al3+ is further away from the nucleus. D The successive IE of these elements increase because the shielding effect increases. Ans C F+: 1s22s22p4 Al2+: 1s22s22p63s1 Option A is incorrect. A l2+ has a higher nuclear charge than F + but the 3 rd electron that is removed from Al is also further away from nucleus than the 2 nd electron that is removed from F. Hence it experiences weaker electrostatic forces of attraction and the 3 rd ionisation energy of Al is lower than 2nd ionisation energy of F. Na+: 1s22s22p6 Mg+: 1s22s22p63s1 Option B is incorrect. The 2nd ionisation energy of Mg is lower than Na because the 3s electron to be removed from Mg+ is at a higher energy level/further away from the nucleus.

3 ASRJC JC2 PRELIMS 2023 9729/01/H2 [Turn over B3+: 1s2 Al3+: 1s22s22p6 Option C is correct. As can be seen from the electronic configuration, the 2p el ectron to be removed from Al3+ is further away/at a higher energy level compared to the 1s electron to be removed from B3+. Option D is incorrect. As electrons are successively removed from the atom, number of protons remains the same ⇒ nuclear charge remains the same. Number of electrons decreases and could be removed from different shell and/or subshell ⇒ shielding effect decreases. Remaining electrons experience strong attraction by the nucleus. More energy is required to remove the electron leading to an increase in I.E. 3 Which statement about the electrons in a ground state germanium atom is correct? A Electrons are present in four different energy levels. B There are more electrons in d orbitals than there are in p orbitals. C The occupied orbital of highest energy is spherical. D The occupied orbital of lowest energy is spherical. Ans D 1s22s22p63s23p63d104s24p2 Statement A is incorrect as electrons are present in eight different energy levels. Statement B is incorrect as there are more electrons in p orbitals (14) than in the d orbitals (10). Statement C is incorrect as the highest energy is 4p orbital which is not spherical.

4 ASRJC JC2 PRELIMS 2023 9729/01/H2 4 Which species contains three π bonds? 1 Al2Cl6 2 SO3 3 CH3CH2COOH 4 CH2CHCH2CN A 2 and 3 B 2 and 4 C 1 only D 2 only Ans B Al2Cl6 8  bonds SO3 3  bonds, 3  bonds CH3CH2COOH 10  bonds, 1  bond CH2=CHCH2C≡N 9  bonds, 3  bond 5 The shape and polarity of four molecules are shown in the following table. Which row is correct? molecule molecular shape polarity A B C D beryllium chloride phosphorus trichloride carbon dioxide tribromomethane bent trigonal pyramidal linear tetrahedral non-polar non-polar polar polar Ans D BeCl2 PCl3 CO2 CHBr3 No. of bp, lp on central atom 2 bp, 0 lp 3 bp , 1 lp 2 bp, 0 lp 4 bp, 0 lp Molecular shape linear trigonal pyramidal linear tetrahedral Be ClCl P Cl Cl Cl C OO C Br Br Br H polarity non–polar polar non-polar polar

5 ASRJC JC2 PRELIMS 2023 9729/01/H2 [Turn over 6 Water, methanol and sulfur dioxide have similarly shaped molecules. O H H O H CH3 S O O What is the strongest intermolecular force in water, methanol and sulfur dioxide? H2O CH3OH SO2 A B C D hydrogen bonds hydrogen bonds permanent dipoles hydrogen bonds hydrogen bonds hydrogen bonds permanent dipoles permanent dipoles permanent dipoles induced dipoles induced dipoles induced dipoles Ans A Presence of H covalently bonded to O and available lone pairs of electrons on O in both water and methanol, hence hydrogen bonds will be the strongest IMF. Sulfur dioxide does not have H covalently bonded to O, hence only permanent dipoles.

6 ASRJC JC2 PRELIMS 2023 9729/01/H2 7 Which graph correctly describes the behaviour of two ideal gases P and Q, both having the same mass, where P has a larger Mr than Q? A B C D Ans B pV = nRT  mRTpV = M  mRp = ( )TVM For graph of p against T, gradient = mR VM Since P has a larger Mr than Q, the graph for P has a less steep gradient. For a fixed mass of gas at constant T, mRTpV = M = constant Hence, the graph of pV against p is a horizontal straight line (option D is incorrect). Since P has a larger Mr than Q, the pV value for P is smaller than that for Q (option C is incorrect). T / oC p Q P T / oC p Q P p V pV constant T Q P p pV constant T P Q T / oC p Q P constant V constant V

7 ASRJC JC2 PRELIMS 2023 9729/01/H2 [Turn over 8 Which gas shows the greatest deviation from ideality? A CH4 B SO3 C C2H2 D CO2 Ans B Deviation depends on IMF and molecular volume. All 4 compounds are non -polar. SO3 has the largest electron cloud size and hence strongest id-id forces of attraction between its molecules, hence deviating greatest from ideal gas behaviour. 9 When 25 cm3 of 0.5 mol dm−3 hydrochloric acid is reacted with an equal volume of 0.5 mol dm−3 potassium hydroxide, the temperature of the mixture rose by 3.4 oC. What will be the temperature change if 50 cm3 of 1 mol dm−3 hydrochloric acid is mixed with an equal volume of 1 mol dm−3 potassium hydroxide? A 1.7 oC B 3.4 oC C 6.8 oC D 13.6 oC Ans C When 25 cm3 of 0.5 mol dm−3 HCl reacted with equal volume of 0.5 mol dm−3 KOH, ∆H1 = − (50 × c × 3.4) / (25 × 10−3 × 0.5) J mol−1 When 50 cm3 of 1 mol dm−3 HCl reacted with equal volume of 1 mol dm−3 KOH,