NJC 2026 Prelim P2 QP

NJC SH2 Prelim 9476/2/26 [Turn over NATIONAL JUNIOR COLLEGE SH2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 2 Structured Questions Candidates answer on Question Paper. Additional Materials: Data Booklet 9476/02 24 Aug 2026 2 hours READ THE INSTRUCTIONS FIRST Write your subject class, registration number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. Marks Weighting Paper 1 /30 15% Paper 2 /75 30% Paper 3 /75 35% Paper 4 /50 20% For Examiner’s Use 1 /8 2 /10 3 /16 4 /17 5 /16 6 /8 Paper 2 Total /75 Overall Percentage Grade This document consists of 28 printed pages (including 3 blank pages).

2 NJC SH2 Prelim 9476/2/26 1 Elements in Period 3 of the Periodic Table show trends in their properties. (a) Fig. 1.1 shows the ionic radii of the anions and cations of Period 3. Atomic number Fig. 1.1 Explain the shape of the graph in Fig. 1.1. …..………………………………………………………………………….….….………..……… …..………………………………………………………………………….….….………..……… …………………………………………………………………………….…..…………………… …………………………………………………………………….………………..……………… ……………………………………………………………………………………………….…..… [2] P3– Cl– Si4+ Na+

3 NJC SH2 Prelim 9476/2/26 [Turn over (b) The third ionisation energies of consecutive Period 3 elements represented by letters A to F are shown in Fig. 1.2. Third ionisation energy A B C D E F Fig. 1.2 Elements (i) Write an equation, including state symbols, to represent the third ionisation energy of element, B. …….......................................................................................................................[1] (ii) Identify which element is phosphorus. Explain your answer. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. [2]

4 NJC SH2 Prelim 9476/2/26 (c) Carbon tetrachloride, CC l4, and phosphorus pentachloride, PC l5, are both non -metal chlorides. (i) When added to water, PCl5 undergoes hydrolysis while CCl4 does not. Explain the difference in behaviour of both chlorides. ……………………………………………………….……………………………………… ………………………………………………………………………………………………. ………………………………………………………………………………………………. [1] (ii) Write a balanced equation for the hydrolysis of PCl5 with water. ……………………………………………………………………………………………[1] Phosphorus pentachloride exhibits distinct structural behaviors depending on its physical state. In the gas and liquid phases, PC l5 exists as discrete covalent molecules, while in solid phase, it exists as giant ionic lattice structure. (iii) When PCl5 solidifies, it undergoes auto-ionisation to form two distinct ions, both of which contain phosphorus and chlorine atoms only. Suggest the formulae of the two oppositely charged ions. cation: ………………….. anion: ………………….. [1] [ Total:8]

5 NJC SH2 Prelim 9476/2/26 [Turn over 2 Hydrogen halides are important industrial chemicals used in processes such as etching, synthesis, and chemical manufacture. (a) The boiling points of hydrogen iodide, HI, and hydrogen chloride, HC l, are as shown in Table 2.1. Table 2.1 Species Boiling Point / C HI –35.4 HCl –85.1 (i) Explain the difference in the boiling points observed for HI and HCl. ……………………………………………………………………………….……….….…. ………………………………………………………………………………………………. …………………………………………………………………………………………...…. [1] (ii) A 25.0 cm3 sample of 0.2 mol dm–3 HI (aq) has a pH of 0.70 at 298 K. State the pH of a 25.0 cm 3 sample of HC l (aq) of the same concentration and temperature. Explain your answer. …………………………………………………………………………………...…………. .…………………………………………………………………………………...………… .……………………………………………………………………………………...……… [1] Hydrogen iodide can react with alcohols to form alkanes under suitable conditions. CH3OH + 2HI CH4 + I2 + H2O (iii) Suggest the role of HI in this reaction. …………………………………………………………………………………………….. ………………………………………………………………………………………….…. .………………………………………………………………………………………… [1]

6 NJC SH2 Prelim 9476/2/26 (b) Hydrogen fluoride, HF, has a very low acid strength. The dissociation of HF in aqueous solution involves a series of steps. HF(aq) H+(aq) + F–(aq) Hdissociation The Hdissociation can be calculated using the enthalpy change of hydration for H+ and F– ions and other data found in Table 2.2. Table 2.2 H / kJ mol–1 first electron affinity for F(g) –328 HF(g) → HF(aq) –48 enthalpy change of hydration for H+ ion –1091 enthalpy change of hydration for F– ion –515 (i) Explain what is meant by enthalpy change of hydration for F– ion. …………………………………………………………………………………………….. ………………………………………………………………………………………….…. [1]

7 NJC SH2 Prelim 9476/2/26 [Turn over (ii) Complete the energy level diagram in Fig. 2.3 and calculate the Hdissociation for HF, using data from Table 2.2 and the Data Booklet. Fig. 2.3 [3]

8 NJC SH2 Prelim 9476/2/26 (iii) Calculate the pH for a 25.0 cm3 sample of 0.20 mol dm –3 HF (aq), given that pKa of HF = 3.14 at 25oC. [1] (iv) Neutron diffraction studies of solid HF show that there are two different distances between hydrogen and fluorine nuclei, 0.092 nm and 0.163 nm. Draw a diagram containing two HF molecules and suggest a reason for the two different distances. Your diagram should show and label both distances. [2] [Total: 10]

9 NJC SH2 Prelim 9476/2/26 [Turn over 3 The chemistry of titanium is of significant industrial importance. (a) (i) Write the electronic configuration of the titanium atom, and hence explain why titanium exhibits a range of oxidation states in its compounds. …………………………………………………………...………………………………….. ………………………………………………………………………...………………….…. ………………………………………………………………………………………...…….. [2] (ii) Complete Fig. 3.1 to show the splitting of energy levels of the