ASRJC 2024 H1Chem Prelim P1 Q&S

ASRJC JC2 Prelim 2024 8873/H1 [Turn over ANDERSON SERANGOON JUNIOR COLLEGE 2024 JC 2 PRELIMINARY EXAMINATION NAME:______________________________ ( ) CLASS: 24 / ___ CHEMISTRY 8873/01 Paper 1 Multiple Choice 17 September 2024 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 and class on the Answer Sheet in the spaces provided. 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 __ printed pages. Multiple Choice Answer Sheet Write your name, class and NRIC / FIN number, including the reference letter. Shade the NRIC / FIN number. Exam Title: JC2 Preliminary Exam Exam Details: H1 Chemistry / Paper 1 Date: 17/09/2024

2 ASRJC JC2 Prelim 2024 8873/H1 1 Use of the Data Booklet is relevant to this question. A proton and a helium nucleus both move at the same speed perpendicular to a uniform electric field. Which row describes the behaviour of the proton and the helium nucleus? A They are deflected in opposite directions. The helium nucleus is deflected most. B They are deflected in opposite directions. The proton is deflected most. C They are deflected in the same direction. The helium nucleus is deflected most. D They are deflected in the same direction. The proton is deflected most. Answer: D Proton is 1H+. Helium nucleus is 4He2+. NOT A and B Both are positively charged so they are deflected in the same direction towards the negatively charged plate. NOT C Proton (1H+) is deflected most. 1H+ 4He2+ charge mass   ratio 1 ½ Angle of deflection is proportional to charge mass ratio. Angle of deflection of 1H+ is twice that of 4He2+. 2 Which of these atomic orbitals possesses the highest relative energy? A 2pz B 3px C 3py D 4s Answer: D The 4 th quantum number possesses larger relative energies as compared to 2 nd and 3 rd quantum shells.

3 ASRJC JC2 Prelim 2024 8873/H1 [Turn Over 3 The 7th, 8th, 9th and 10th ionisation energies of an element are shown. 7th ionisation energy / kJ mol−1 8th ionisation energy / kJ mol−1 9th ionisation energy / kJ mol−1 10th ionisation energy / kJ mol−1 9941 18 580 21 610 25 180 Which group does this element belong to? A 15 B 16 C 17 D 18 Answer: C Largest difference in ionisation energy (IE) is between the 7 th and 8 th electron removed, indicating 7 valence electrons and the 8 th electron is removed from an inner quantum shell. Thus, the element is from Group 17. 4 Silicon carbide, SiC, is a shiny, hard, chemically inert material with a very high melting point. It can be used to sharpen knives and make crucibles. Which type of structure does silicon carbide have? A a giant structure with covalent bonds between silicon and carbon atoms B a giant structure containing strong electrostatic forces of attraction between oppositely charged ions C a giant layered structure with covalent bonds between atoms and instantaneous dipole – induced dipole forces between layers D a simple molecular structure with covalent bonds between the atoms of silicon and carbon Answer: A A Correct. Strong covalent bonds between the non -metallic atoms in an extensive 3 - dimensional network. B Incorrect. Silicon and carbon are non -metallic elements. Moreover, giant ionic compounds tend to be brittle and unable to be used to sharpen knives and crucibles. C Incorrect. This is the description for graphite. The instantaneous dipole – induced dipole forces will cause the layers to slip over one another and the resultant compound is not expected to be hard. D Incorrect. Simple molecules have weak intermolecular forces of attraction and which are easily broken.

4 ASRJC JC2 Prelim 2024 8873/H1 5 Compared with the HCl molecule, the bond ….X..... of the HI molecule is ….Y….. Which pairs of words correctly complete the above sentence? X Y 1 energy greater 2 length longer 3 polarity lower A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only Answer: C • Size of valence orbitals: I > Cl • Valence orbitals of I are more diffused than that of Cl • Overlap of orbitals is less effective in H–I than in H–Cl • H−I bond is weaker than H−Cl bond Hence, bond energy: H−I < H–Cl; bond length: H−I > H–Cl • Electronegativity: I < Cl Hence, H−I bond is less polar than H–Cl bond

5 ASRJC JC2 Prelim 2024 8873/H1 [Turn Over 6 The diagram below shows the structure of part of a crystal of ice. O H H H H O H O H H O H H H O H O H O H H Which statement is correct? A All the bond angles surrounding each oxygen atom are 120°. B Four electrons from each oxygen are involved in forming hydrogen bonds. C The hydrogen bonds, shown by the dotted lines, are stronger than the O‒H covalent bonds. D The open structure of ice causes ice to be denser than water. Answer: B Option A is incorrect as all the bond angles surrounding each O atom are 109.5o (tetrahedral). Option B is correct as 2 lone pairs (total 4 electrons) on each O atom are used to form H-bonds with H from neighboring H2O molecules. Option C is incorrect as hydrogen bonds are weak intermolecular forces compared to covalent bonds which are stronger. Option D is incorrect as open structure i.e. lots of empty space between molecules is the reason why the density of ice is lower than that of water.

6 ASRJC JC2 Prelim 2024 8873/H1 7 The ionic product of water, Kw, is affected by temperature. Temperature / oC Kw x 10−14 / mol2 dm−6 10 0.293 40 2.92 Which statement describes what happens as the temperature of water is increased from 10 oC to 40 oC? A pH of water decreases and [H+] = [OH−]. B pH of water decreases and [H+] is greater than [OH−]. C pH of water increases and [H+] = [OH−]. D pH of water increases and [H+] is less than [OH−]. Answer: A H2O H+ + OH− H > 0 Kw = [H+][OH−] When temperature of water increases, Kw also increases. This shows that the position of equilibrium has shifted to the right and more H+ and OH− ions are produced. pH = –log10 [H+]  pH of water decreases Since the stoichiometric coefficients of H + and OH− ions are equal in the above equation, the increase in the number of H+ and OH− ions will be the same.  [H+] = [OH−]

7 ASRJC JC2 Prelim 2024 8873/H1 [Turn Over 8 25.0 cm3 of 0.100 mol dm –3 phosphoric acid, H 3PO4, is titrated against 0.100 mol dm –3 NaOH. The following pH value is recorded. Volume of NaOH added/ cm3 pH 25.00 4.70 The table below shows the pH range for colour change for some acid-base indicators. indicator range