2025 CHIJ SEC (TP) Chemistry Prelim Paper 2 QP

O CONVENT OF THE HOLY INFANT JESUS SECONDARY Preliminary Examination in preparation for the General Certificate of Education Ordinary Level 2025 CANDIDATE NAME CLASS REGISTER NUMBER CHEMISTRY Paper 2 Candidates answer on the Question Paper. No Additional Materials are required. 6092/02 28 August 2025 1 hour 45 minutes READ THESE INSTRUCTIONS FIRST Write your name, class and register number on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 24. The use of an approved scientific calculator is expected, where appropriate. This document consists of 24 printed pages. [Turn over

2 CHIJSec/2025/OLevelPrelim/6092/02 Section A Answer all questions. 1 Fig. 1.1 shows some elements in the Periodic Table. H Li F Mg Ar Zn Br Ag Fig. 1.1 Use the symbols from the table to identify the following elements. Each element may be used once, more than once or not at all. (a) This element forms an amphoteric oxide. ……………………………………………………………...………………………………..….. [1] (b) This element has a melting point below room temperature but a boiling point above room temperature. ……………………………………………………………...………………………………..….. [1] (c) This is the least reactive element in its group. ……………………………………………………………...………………………………..….. [1] (d) This element is used to provide an inert environment in industrial reactions. ……………………………………………………………...………………………………..….. [1] (e) This element forms coloured compounds. ……………………………………………………………...………………………………..….. [1] [Total: 5]

3 CHIJSec/2025/OLevelPrelim/6092/02 [Turn over 2 Chromatography can be used to separate and identify components of a mixture. Synthetic dyes are examples of mixtures that can be separated using paper chromatography. A student wanted to find out whether a sample of black dye is pure. She carried out the following procedure: Step 1: A start line was drawn using a pencil, on a sheet of chromatography paper. Step 2: She placed spots of known dyes, A, B, C, D and E and the black dye on the start line. Step 3: The chromatography was allowed to run using ethanol as a solvent. Fig. 2.1 shows the results of the experiment. Fig. 2.1 (a) Using the results of the chromatography in Fig . 2.1, explain whether the sample of black dye is pure. …………………………………………………….……….……………………………………….. ……………………………………………………………...………………………………..….. [1] (b) Suggest another method that the student can use to determine whether the sample of black dye is pure. State the expected observations clearly. …………………………………………………….……….……………………………………….. ……………………………………………………………...………………………………..….. [2] (c) Explain why dye B remains on the starting line at the end of the experiment. ……………………………………………………………...………………………………..….. [1] solvent front starting line position of black dye at the start A B C D E 8 7 6 5 4 3 2 1 0 cm

4 CHIJSec/2025/OLevelPrelim/6092/02 (d) In chromatography, Rf values can be used to identify substances. The Rf value of an industrial dye, safranin, in ethanol is 0.45. Using the results from Fig 2.1, suggest which of the dyes, A, B, C, D, or E could be safranin. Show your working clearly. dye ……………………. working [2] [Total: 6]

5 CHIJSec/2025/OLevelPrelim/6092/02 [Turn over 3 Table 3.1 shows information about some gases in the atmosphere of the planets Mars and Earth. Table 3.1 gas density of pure gas at room temperature and pressure in g/dm3 percentage composition of atmosphere on Mars (%) percentage composition of atmosphere on Earth (%) argon 1.67 1.9 <1 carbon dioxide 1.83 95.1 0.04 nitrogen 1.17 2.6 oxygen 0.2 other gases − <1 <1 (a) Complete the last column of Table 3.1. [1] (b) Calculate the density of pure oxygen at room temperature and pressure in g/dm3. density of oxygen ……………… g/dm3 [1] (c) In Table 3.1 , the term ‘other gases’ includes n itrogen oxides (NOx). NO and NO 2 are examples of nitrogen oxides. (i) Scientists have found much more nitrogen oxides in the atmosphere of Earth than on Mars. Use the information in Table 3.1 and your knowledge about how nitrogen oxides are formed to suggest why this is so. …………..………………………………………………………………...……………......... …………..………………………………………………………………...……………......... …………..………………………………………………………………...……………......... …………..………………………………………………………………...…………….... [2]

6 CHIJSec/2025/OLevelPrelim/6092/02 (ii) The breakdown of ozone, O3, is typically a slow process. Nitrogen oxides such as nitrogen monoxide, NO, in the upper atmosphere can cause damage to the ozone layer by rapidly reacting with ozone in a two-step reaction. Step 1 NO + O3 → NO2 + O2 Step 2 NO2 + O3 → NO + 2O2 Use the equations to explain how nitrogen monoxide acts as a catalyst for the breakdown of ozone. …………..………………………………………………………………...……………......... …………..………………………………………………………………...……………......... …………..………………………………………………………………...…………….... [2] (d) Scientists predicted the surface temperature on Mars by calculating its distance from the Sun. The measured surface temperature is higher than the predicted value. Use the information in Table 3.1 to suggest a reason why the measured surface temperature of Mars is higher than its predicted temperature. ………………………………………………………………..…………………………………….. ……………………………………………………………...………………………………..…. [1] [Total: 7]

7 CHIJSec/2025/OLevelPrelim/6092/02 [Turn over 4 Fig. 4.1 shows an electrolysis experiment made up of two cells. Fig. 4.1 Electrodes W, X, Y and Z are made of graphite. (a) (i) Give the half-equations for the reactions at electrodes Y and Z in cell 2. electrode Y: …………………………………………………………………………….. [1] electrode Z: …………………………………………………………………………….. [1] (ii) Describe and explain the colour change of the Universal Indicator in cell 2 during the electrolysis. …………..………………………………………………………………...……………......... …………..………………………………………………………………...……………......... …………..………………………………………………………………...……………......... …………..………………………………………………………………...…………….... [2] cell 1 cell 2 Y Z + − dilute aqueous copper(II) sulfate concentrated aqueous potassium chloride and Universal Indicator W X

8 CHIJSec/2025/OLevelPrelim/6092/02 (b) Electrodes W and X are replaced with copper electrodes. Give one similarity and one difference in the observations in cell 1 when copper electrodes are used as compared to when graphite electrodes are used. Explain your reasoning. ………………………………………………………………………………………………………. …………………………………………………………………………………………………….... ………………………………………………………………………………………………………. …………………………………………………………………………………………………….... ………………………………………………………………………………………………………. …………………………………………………………………………………………………….... …………………………………………………………………………………………………….... ……..……………………………………………………………………………………………. [4] [Total: 8]

9 CHIJSec/2025/OLevelPrelim/6092/02 [Turn over 5 The apparatus shown in Fig. 5.1 is used to investigate the reduction of a metal oxide by hydrogen. Hydrogen gas is passed over the heated metal oxide in a boiling tube. The unreacted hydrogen gas is burnt as it leaves the tube. Fig. 5.1 (a) An oxide of iron