2022 PLMGS Chem Prelims P1

1 [Turn over CANDIDATE NAME CLASS CLASS INDEX NUMBER CENTRE NUMBER INDEX NUMBER CHEMISTRY 6092/01 Paper 1 Multiple Choice 26 August 2022 1 hour Additional Materials: Multiple Choice Answer Sheet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, class and class index number on the separate Answer Sheet in the spaces provided. There are forty 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. 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 paper. A copy of the Periodic Table is printed on page 2. The use of an approved scientific calculator is expected, where appropriate. This document consists of 17 printed pages, including the cover page. Paya Lebar Methodist Girls’ School (Secondary) Preliminary Examination 2022 Secondary 4 Express

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4 Use the following information to answer Questions 1 and 2. When solid hydrated barium hydroxide is added to a known quantity of solid ammonium chloride, the temperature of the mixture decreases. The chemical reaction is represented by the balanced chemical equation shown below. Ba(OH)2.8H2O (s) + 2NH4Cl (s) 2NH3 (g) + 10H2O (l) + BaCl2 (s) 1 An experiment is designed to measure the temperature change when all the solid hydrated barium hydroxide reacts with the ammonium chloride. The following pieces of apparatus are available. 1 gas syringe 2 stopwatch 3 balance 4 Styrofoam cup Other than a thermometer, which piece(s) of apparatus is(are) likely needed for this experiment? A 1, 2 and 3 only B 1 and 2 only C 3 and 4 only D 4 only 2 Which diagram shows the correct way of drying and collecting the gas produced? A B C D gas concentrated sulfuric acid calcium oxide gas gas concentrated sulfuric acid calcium oxide water gas

5 [Turn over 3 A solution of X is added to 1 cm3 of sulfuric acid. Effervescence is seen. The gas produced is bubbled into a test tube of limewater. The following observation is made. What could X be? A barium carbonate B sodium hydroxide C barium nitrate D sodium carbonate white precipitate limewater

6 4 The apparatus shown is used to distil pentanol (boiling point 138 oC) from a mixture of water and pentanol. Which graph shows the change in concentration of the pentanol in flask F as the distillation proceeds? A B C D water out water in heat mixture of water and pentanol thermometer fractionating column flask F time concentration of pentanol time concentration of pentanol time concentration of pentanol time concentration of pentanol

7 [Turn over 5 The diagram shows the experimental set-up to investigate the movement of gases A and B. After a while, the water on the left side of the U-shaped tube moved up. If gas A is fluorine, what could gas B be? A chlorine B carbon dioxide C neon-19 D argon-38 6 Four elements are shown as P, Q, R and S. The letters do not represent the chemical symbols of the elements. An ion is formed from the atom of one of the four elements. The ratio of the number of atoms to the number of electrons gained is 1:2. The ion formed consists of 2 electron shells. Which element is the ion formed from? A 1224𝑃 B 818𝑄 C 1632𝑅 D 410𝑆 7 Which two substances have similar molecular structures? A sodium chloride and potassium chloride B silicon and diamond C carbon dioxide and sodium oxide D diamond and methane large beaker A B porous pot U-shaped tube water

8 8 The following diagram shows the structure of substance Y. What could substance Y and particles A and B be? substance Y particle A particle B A potassium chloride anion cation B graphite electron atom C potassium electron cation D copper electron cation 9 A caffeine molecule has the following structure as shown below, with three unknown elements R, T and X. H represents hydrogen atoms. What could element R, S and X be? R T X A sulfur carbon silicon B oxygen carbon chlorine C chlorine boron carbon D oxygen nitrogen carbon 10 20 cm3 of dilute phosphoric acid, H3PO4, contains 0.04 mol of the acid. Assuming that phosphoric acid ionises completely in a reaction with sodium hydroxide, what is the concentration of the hydrogen ions in the solution? A 0.67 mol/dm3 particle A particle B T T T T

9 [Turn over B 2.00 mol/dm3 C 4.00 mol/dm3 D 6.00 mol/dm3 11 Fluorine reacts with nitrogen dioxide according to the equation below. F2 (g) + 2NO2 (g) → 2NO2F (g) If 90 cm3 of gaseous fluorine is mixed with 110 cm3 of gaseous nitrogen dioxide, what is the total volume of the resultant mixture at room temperature and pressure? A 55 cm3 B 110 cm3 C 145 cm3 D 165 cm3 12 Anhydrous washing soda, Na2CO3, is a component of many dry soap powders. The remaining mass of the anhydrous sample after a hydrated sample, Na2CO3.10H2O, is heated to dryness is 15.3 g. What is the mass of oxygen found in the hydrated sample, Na2CO3.10H2O? [Mr of anhydrous Na2CO3 is 106; Mr of H2O is 18] A 9.24 g B 23.1 g C 30.0 g D 81.0 g 13 In an electrolysis of an aqueous solution, what effect could increasing its concentration have? A The product at the cathode may change. B The product at the anode may change. C Products at both electrodes may change. D There is no effect on the products formed. 14 Which of the following correctly describes the electrolysis of molten zinc chloride? product formed at the negative electrode product formed at the positive electrode terminal of the dry cell that electrons flow out of A zinc chlorine negative B chlorine zinc negative C zinc chlorine positive D chlorine zinc positive

10 15 The equation for the addition reaction of ethene is shown. C2H4 + H2 C2H6 ∆𝐻 = -127 kJ/mol C–H H–H C–C bond energy in kJ/mol 413 432 347 What is the energy of the C=C bond found in ethene? A 307 kJ/mol B 582 kJ/mol C 614 kJ/mol D 768 kJ/mol 16 The energy profile diagram for the forward reaction in a reversible reaction is shown. Which statement about the energy profile diagram is correct? A The enthalpy change is the difference between x and y. B The value of y is unaffected by the addition of a catalyst. C The value of x remains the same when a catalyst is added. D The activation energy of the backward reaction is y – x. 17 Which pair of substances, when mixed together, will produce the lowest initial rate of reaction? volume of nitric acid / cm3 concentration of nitric acid / cm3 size of zinc A 30 0.1 powder B 30 0.2 granules C 120 0.2 powder energy progress of reaction x y