ACJC H1 CHEM P1

ANGLO-CHINESE JUNIOR COLLEGE DEPARTMENT OF CHEMISTRY Preliminary Examination CHEMISTRY 8872/01 Higher 1 Paper 1 Multiple Choice 02 September 2015 50 minutes Additional Materials: Multiple Choice Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluids. Write your name, index number and tutorial class 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 booklet. The use of an approved scientific calculator is expected, where appropriate. This document consists of 14 printed pages and 2 blank pages. 8872/Prelims/15 ANGLO-CHINESE JUNIOR COLLEGE © ACJC 2015 Department of Chemistry [Turn over

© ACJC 2015 8872/01/Prelim/15 [Turn over 2 Section A For each question there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 Tetraarsenic trisulfide, As4S3 is used as a maintenance therapy for newly diagnosed acute leukemia. It reacts with oxygen to produce an oxide of arsenic in the +5 oxidation state and an oxide of sulfur in the +4 oxidation state. How many moles of oxygen gas are needed to burn two moles of As4S3? A 7.5 B 8 C 15 D 16 2 In an experiment, 33.40 cm 3 of a 0.150 mol dm −3 solution of a metallic ion, M n+, reacted exactly with 50.0 cm3 of 0.050 mol dm−3 aqueous sodium sulfite. The half-equation for the oxidation of sulfite ion is shown below. SO3 2− (aq) + H2O (l)  SO4 2− (aq) + 2H+ (aq) + 2e− If the final oxidation number of the metal in the salt was +3, what would be the original oxidation number of the metal? A +2 B +3 C +4 D +5 3 Titanium has the electronic structure, 1s2 2s2 2p6 3s2 3p6 3d2 4s2. Which one of the following compound is NOT likely to exist? A TiN B KTiO4 C TiS D Na3TiF6

© ACJC 2007 9746/01/Prelim/07 [Turn over 3 4 The successive ionisation energies, in kJ mol–1, of an element X are given below. 1010 2265 3662 4998 7002 8992 28698 32215 Which one of the following would best represent the formula of the ionic compound formed by X? A XBr B XO2 C MgX2 D K2X 5 Which molecule has the largest dipole? A B C D 6 Which of the following pairs of substances have different types of bonding and structure? A AsCl3 AsCl5 B AlF3 AlCl3 C P4 PH3 D Si SiO2 7 Which of the following cannot be explained by hydrogen bonding? A Ethanoic acid molecules form dimers in presence of benzene. B Boiling point of alcohols increases with increasing Mr. C Ice can float on frozen lake. D Formation of HF2 ¯.

© ACJC 2015 8872/01/Prelim/15 [Turn over 4 8 A student weighed 4.20 g of solid sodium hydrogencarbonate, NaHCO 3 (Mr = 84.0), and dissolved it completely in 50 cm3 of water. The drop in temperature was 3.8 oC. What is the enthalpy change of this reaction in kJ mol–1? (The specific heat capacity of solution is 4.18 J cm–3 oC–1) A 1000 3.8 x 4.18 x 4.2      B 1000 x 4.2 84.0 x 3.8 x 4.18 x 50       C 1000 3.8 x 4.18 x 50      D 1000 x 4.2 84.0 x 3.8 x 4.18 x 4.2       9 The kinetics of the reaction between thiosulfate ions and acid is studied by varying the concentrations and measuring the time taken for the ‘cross’ to be totally obscured by the sulfur produced. The results are recorded in the table below. S2O3 2–(aq) + 2H+(aq)  H2O(l) +SO2(g) + S(s) Experiment Vol of S2O3 2– /cm3 Vol of H+/cm3 Vol of H2O/cm3 Time taken/min 1 30 30 10 11.0 2 30 40 0 10.0 3 45 20 5 6.5 What is the order of reaction with respect to each of the reactant? Order with respect to S2O3 2– Order with respect to H+ A 0 1 B 1 0 C 1 1 D 2 0

© ACJC 2007 9746/01/Prelim/07 [Turn over 5 10 The reaction of hydrogen peroxide with iodide ions in acidic medium is as shown: H2O2(aq) + 2H+(aq) + 2I ˉ(aq)  2H2O(l) + I2(aq) It is found that the order of reaction with respect to hydrogen peroxide and iodide ions is 1 respectively. The product of concentrations of hydrogen peroxide and iodide ions is plotted against time, t for the following reaction. Which of the following graph is obtained? A B C D

© ACJC 2015 8872/01/Prelim/15 [Turn over 6 11 W and Y are mixed in a vessel to form X as shown. At time t min, the equilibrium mixture is subjected to a change. 2W(g) + Y(g) 2X(g) ΔH < 0 Which of the following changes made would result in the graph above? A Decrease the temperature. B Decrease the volume of container. C Add 1 mol of neon gas. D Add 1 mol of X(g). 12 Water dissociates into H+ and OH– as shown. H2O H+ + OH– At 25 °C, the equilibrium [H+] is 10–7 mol dm–3; density of H2O = 1 kg dm–3. What is the order of increasing numerical value of pH, pKa and pKw for this equilibrium at this temperature? A pH, pKa, pKw B pH, pKw, pKa C pKa, pKw, pH D pKw, pKa, pH X Y W Concentration Time t

© ACJC 2007 9746/01/Prelim/07 [Turn over 7 13 An enzyme required in laboratory process operates at maximum efficiency when placed in an aqueous solution buffered at pH 5.6. Which combination of substances when dissolved in water would give the appropriate buffer solution? A 0.5 mol of HCl and 1 mol of CH3COOH B 0.5 mol of HCl and 1 mol of CH3COONa C 1 mol of CH3COOH and 1 mol of NaOH D 1 mol of CH3COONH4 14 Which factor helps to explain why the first ionisation energies of the Gr oup II elements decrease from beryllium to magnesium to calcium to strontium? A The nuclear charge of the elements increases. B The shielding effect of the inner shells increases. C The outer electron is in ‘s’ subshell. D The repulsion between spin–paired electrons increases. 15 P, Q and R are consecutive elements in Period 3 of the Periodic Table. Q has the highest first ionisation energy and the lowest melting point among the three elements. Which of the following could be P, Q and R? A aluminium, silicon, phosphorus B sodium, magnesium, aluminium C magnesium, aluminium, silicon D silicon, phosphorus, sulfur 16 Element S is found in Period 3 of the Periodic Table. The oxide and chloride of element S are separately mixed with water . The two resulting solutions have the same effect on universal indicator. What is the identity of element S? A Sodium B Magnesium C Aluminum D Phosphorous

© ACJC 2015 8872/01/Prelim/15 [Turn over 8 17 Cholesterol is the most common steroid alcohol. It has a molecular formula of C 27H46O and has the structure shown. How many carbon atoms are in the hydrocarbon group R? A 7 B 8 C 9 D 10 18 Which property of benzene may be directly attributed to the stability associated with its delocalised electrons? A It has a low boiling point. B It tends to undergo substitution rather than addition reactions. C It does not conduct electricity. D It does not react with sodium.

© ACJC 2007 9746/01/Prelim/07 [Turn over 9 19 Jasmone is an active ingredient of jasmine. It is extracted from jasmine flowe rs for perfume.