2024 Prelims EJC H2 Chem P1 (QP)

© EJC [Turn Over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examination 2024 General Certificate of Education Advanced Level Higher 2 CHEMISTRY Paper 1 Multiple Choice 9729/01 18 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, civics group and registration number on the Answer Sheet in the spaces provided unless this has been done for you. 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 question paper. The use of an approved scientific calculator is expected, where appropriate. This document consists of 12 printed pages.

2 © EJC 9729/01/J2PE/24 1 A gravimetric analysis of a sample of an iron ore was carried out. 0.6 g of ore was dissolved in perchloric acid to oxidise the iron to Fe 3+. The resultant solution was filtered to remove solid impurities and made basic to precipitate the Fe3+ as the hydroxide. The precipitate was filtered and heated to produce 0.32 g of Fe2O3. What is the percentage by mass of iron in the ore? A 18.6% B 37.3% C 53.0% D 69.9% 2 Ions of element Y can exist in variable oxidation states. 25.0 cm 3 of 0.400 mol dm –3 Y2+ solution requires 40.00 cm3 of 0.100 mol dm–3 acidified KMnO4 for a complete reaction. What is the final oxidation state of Y? A +4 B +3 C 0 D −1 3 Which of the following ions would experience the greatest angle of deflection in its path when passing through the same electric field? A 24Mg+ B 48Ti3+ C 59Co2+ D 101Ru4+ 4 Which of the following shows the correct shape and bond angle of the molecule given? molecule shape bond angle A OF2 bent 117º B BF3 trigonal pyramidal 120º C XeF4 tetrahedral 109.5º D SF6 octahedral 90º

3 © EJC 9729/01/J2PE/24 [Turn over 5 Ideal gases K and L, initially at different pressures and temperatures, are placed in different bulbs that are connected by a narrow tube of negligible volume as shown. When the tap is opened, the gases mix. What is the final pressure of the mixture if both bulbs are maintained at 227 ºC? A 28.0 kPa B 30.0 kPa C 36.6 kPa D 68.6 kPa 6 The enthalpy changes involved in the formation of KC l(aq) from K(s) and C l2(g) are as follows: Which of the following statements are correct? 1 The lattice energy of potassium chloride is ∆H3. 2 The enthalpy change of solution of potassium chloride is (∆H3 + ∆H4). 3 The enthalpy change of formation of solid potassium chloride is (∆H1 + ∆H2 + ∆H3). A 1 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3 gas K 100 cm3 40 kPa 227 ºC gas L 400 cm3 20 kPa 127 ºC K(s) + Cl2(g) K(g) + Cl(g) K+(g) + Cl–(g) KCl(s) K+(aq) + Cl–(aq) H1 H2 H3 H4

4 © EJC 9729/01/J2PE/24 7 In this question, the symbol ‘<’ means ‘less positive than’ or ‘more negative than’. Silver chloride dissolves in dilute NH 3(aq) whereas silver bromide is only soluble in concentrated NH3(aq). The following equations represent the equilibria involved. AgCl(s)  AgCl(aq) G1 AgCl(aq) + 2NH3(aq)  Ag(NH3)2Cl(aq) G2 AgBr(s)  AgBr(aq) G3 AgBr(aq) + 2NH3(aq)  Ag(NH3)2Br(aq) G4 Some relationships between the free energies of these four reactions are as follows. 1 (G1 + G2) < (G3 + G4) 2 G2 = G4 3 G2 < G4 4 G1 < G3 Which relationships are correct? A 1, 2 and 4 only B 1 and 3 only C 2 and 4 only D 3 only 8 Photochromic glass is used in transition lens. It quickly darkens when exposed to UV light and slowly becomes more transparent again when the intensity of UV light decreases. The depth of colour of the glass is proportional to the concentration of silver atoms present. The following reactions are involved: reaction 1 Ag+ + Cl–  Ag + Cl reaction 2 Cu+ + Cl → Cu2+ + Cl– reaction 3 Cu2+ + Ag → Cu+ + Ag+ Which statement about these reactions is correct? A Since Cu+ and Cu2+ acts as catalysts, both reactions 2 and 3 are much faster than the forward reaction in Ag+ + Cl–  Ag + Cl when intensity of UV light is high. B The forward reaction in Ag+ + Cl–  Ag + Cl is non-spontaneous. C Reaction 3 is less spontaneous after glass darkens in UV light, as compared to the glass being clear. D The position of equilibrium of reaction 1 shifts to the left in strong UV light.

5 © EJC 9729/01/J2PE/24 [Turn over 9 The distribution of the number of molecules with energy E for an uncatalysed reaction with a given activation energy, Ea, is shown in the diagram below. Which expression gives the fraction of the molecules that results in a reaction occurring when a catalyst is added at the start of the same reaction? A W ZYX ++ B YXW Z ++ C X Y Z W X Y Z ++ + + + D Z W X Y Z+ + + 10 The Kc value of reaction 1 is 2.55 × 1065 at 373 K. Reaction 1 is catalysed by zirconium metal. reaction 1: Y(aq)  2Z(aq) H = +28 kJ mol–1 Which of the following statements regarding reaction 1 are true? 1 The forward reaction proceeds very quickly because the Kc value is very large. 2 The Kc value will increase when boiling water is added and the mixture is kept at 373 K and 1 atm. 3 After the addition of a few granules of zirconium , the Kc value remains at 2.55 × 1065. A 3 only B 1 and 2 only C 2 and 3 only D 1, 2, and 3

6 © EJC 9729/01/J2PE/24 11 Gas A decomposes to two other gases, B and C, according to the following equation: A(g)  2B(g) + C(g) The graph shows the decomposition of 2.0 mol of pure gas A in the presence of a catalyst at various temperatures. Which one of the following statements about the above system is correct? A The decomposition of A is endothermic. B The Kp of the system decreases with increasing temperature. C The percentage of A decomposed is 40% when equilibrium is reached at 650 ºC. D The amount of C at equilibrium is 0.8 mol at 650 ºC. 12 What is the pH of the final solution formed when V dm3 of dilute hydrochloric acid of pH 2.0 is mixed with V dm3 of dilute sulfuric acid of pH 2.0, followed by the addition of 2V dm3 of water? A 1.33 B 2.00 C 2.30 D 4.00 13 A buffer solution consists of an aqueous solution of a weak acid and its sodium salt. Which of the following expressions gives the best estimate of the hydrogen ion concentration? A  aH acid K+ = B  aH salt K+ = C     a acidH saltK+ = D     a saltH acidK+ = amount of A / mol 1.6 2.0 1.2 0.8 0.4 0.0 650 ºC 500 ºC time

7 © EJC 9729/01/J2PE/24 [Turn over 14 Calcium oxalate, CaC 2O4, is a sparingly soluble salt and is added to a weakly acidic solution of oxalic acid, H2C2O4. The pH of the solution is adjusted by adding NaOH. Which diagram shows how the solubility of CaC2O4 will vary with the pH of the solution at constant temperature? A B C D 15 Which property of the first six elements of Period 3 (sodium to sulfur) continuously increases in magnitude? A atomic radius B first ionisation energy C maximum oxidation number in oxide D melting point of the highest chloride 16 Gallstones can form in the gall bladder and are very painful. The inorganic part of gallstones is calcium oxalate, CaC 2O4, which is insoluble in water. The corresponding magnesium oxalate, MgC2O4, is soluble in water. What factor accounts for the difference in solubility between CaC2O4 and MgC2O4? A The entropy change for dissolution of MgC2O4 is more negative than CaC2O4 due to the higher charge density of Mg2+. B Mg2+ ions