ACJC H2 Chem 2013 Prelim P1 QP

© ACJC 2013 9647/01/Prelim/13 [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 10 cm3 of a hydrocarbon was mixed with 100 cm 3 of oxygen gas which was in excess. After explosion and cooling, the gaseous mixture occupied a volume of 80 cm 3. After absorption by aqueous potassium hydroxide, the volume decreased to 50 cm3. What is the formula of the unknown hydrocarbon? A C3H6 B C3H8 C C4H8 D C4H10 2 Ethanenitrile, CH 3CN was boiled with NaOH and the NH 3 gas evolved was passed into 50 cm 3 of 1.00 mol dm -3 of HC l. The excess acid required 26.00 cm3 of 1.00 mol dm-3 NaOH solution for complete neutralisation. What was the mass of ethanenitrile used? A 0.492 g B 0.984 g C 1.07 g D 1.97 g 3 For a given mass of an ideal gas, which one of the following graphs displays a different shape from the rest? A PV against V (at constant T) B PV against P (at constant T) C T V against T (at constant P) D density 1 against T (at constant P) 237

© ACJC 2013 9647/01/Prelim/13 [Turn over 3 4 Xofigo®, containing the radioactive isotope, Ra223 88 , had received United States FDA approval for the treatment of cancer in patients. Ra223 88 decays to give only an element X and a high energy α-particle ( He4 2 ); the latter targets the cancer cells. Ra223 88  X + He4 2 What is the number of neutrons present in element X? A 86 B 133 C 135 D 219 5 Phosphorus oxides exist in many different intermediate forms. Two forms of phosphorus oxides, P4O9 and P4O10, are shown above. Which one of the following statements is true? A The phosphorus atoms of both oxides can act as ligands. B The phosphorus atoms of both oxides have the same oxidation state. C The phosphorus atoms of both oxides do not have lone pair of electrons D The phosphorus atoms of both oxides have electron pairs that are arranged in tetrahedral shape. P O P O PO O O OP O O O P O P O PO O O OP O O O O P4O9 P4O10 238

© ACJC 2013 9647/01/Prelim/13 [Turn over 4 6 Which statement about AlCl3 is correct? A AlCl3 is pyramidal. B AlCl3 has a higher melting point than Al2O3. C Al2Cl6 dimer contains two co-ordinate bonds. D AlCl3 catalyst acts as an electron pair donor in the acylation of benzene. 7 Consider the equation: 2SO2(g) + O2(g) → 2SO3(g) where ∆H = -199 kJ mol-1 and ∆S = -190 J K-1 mol-1. Which of the following statements is correct? A As the reaction proceeds, the system becomes more disorderly. B The products are energetically less stable than the reactants. C As temperature increases, the change in Gibbs free energy becomes more negative. D The reaction is spontaneous under standard conditions. 8 Consider the mechanism of the hydrolysis of 2-methyl-2-bromopropane (RBr) by hydroxide ion below: Step 1: RBr  R+ + Br - (slow) Step 2: R+ + OH-  ROH (fast) Which one of the following correctly represents the units for the rate constant of this reaction? A mol dm-3 s-1 B mol-1 dm3 s C mol-1 dm3 s-1 D s-1 239

© ACJC 2013 9647/01/Prelim/13 [Turn over 5 9 Swimming pool water can be kept free of harmful bacteria by adding aqueous sodium chlorate(I), NaOCl. This reacts with water to produce HOCl molecules which kill bacteria. OCl–(aq) + H2O(l) OH–(aq) + HOCl(aq) In bright sunshine, the OCl– ion is broken down by ultra-violet light. OC l–(aq) Cl–(aq) + ½O2(g) Which method would maintain the highest concentration of HOCl(aq)? A acidify the pool water B add a solution of chloride ions C add a solution of hydroxide ions D bubble air through the water 10 To prepare 'deionised' water, tap water containing ions, including chloride ions, is passed through a column of resin that helps to remove the ions present. If the concentration of chloride ions in the water that leaves the column is high enough to cause the precipitation of silver chloride when 1 cm 3 of the water is added to 1 cm 3 of 1 mol dm -3 silver nitrate solution, the water is no longer considered 'deionised' and hence, the resin in the column has to be replaced. What is the maximum allowed concentration of chloride ions that can be present in the water that leaves the column? [Solubility product of silver chloride : 1.8 x 10 -10 mol2 dm-6] A 1.8 x 10-10 mol dm-3 B 3.6 x 10-10 mol dm-3 C 7.2 x 10-10 mol dm-3 D 1.8 x 10-11 mol dm-3 uv light 240

© ACJC 2013 9647/01/Prelim/13 [Turn over 6 11 The pH range and colour changes for two acid-base indicators are given below: Indicator Colour in acidic solution pH range Colour in basic solution P violet 3.0-5.0 red Q yellow 5.7-7.6 blue Which solution will appear red in P and yellow in Q? A 0.1 mol dm-3 of HCl B 0.1 mol dm-3 of NaOH C 0.1 mol dm-3 of CH3COOH (Ka= 1.8 x 10-5 mol dm-3) D 0.1 mol dm-3 of HX (Ka= 2.5 x 10-10 mol dm-3) 12 The use of Data Booklet is relevant to this question. A cell is set up as shown: Cd(s) | Cd2+(aq) || Ag+(aq) | Ag(s) The following values for the cell potential were determined as a change was continuously made. Readings Cell potential/ V 1 1.200 2 1.081 3 1.064 Which one of the following changes was made? A adding a reagent to the solution that complex with Ag+(aq) B increasing concentration of Ag+(aq) C increasing the surface area of the cadmium immersed in the solution D adding equal amount of water to both half-cells 241

© ACJC 2013 9647/01/Prelim/13 [Turn over 7 13 When a large current was passed through an electrolyte containing chromium(III) ions, there was a simultaneous liberation at the cathode, x mol of chromium and y dm3 of hydrogen (measured at r.t.p.). How many moles of electrons were passed through the solution? A x + y B x + y/24 C 3x + y/24 D 3x + y/12 14 A hydrocarbon, when heated with excess hot acidified concentrated KMnO 4 produces HO2CCH2CH2CH2COCH2CH3. Which one of the structures cannot be the hydrocarbon? A CH2CHCH2CH2CH2C(CH2CH3)CH2 B C D 242

© ACJC 2013 9647/01/Prelim/13 [Turn over 8 15 Limonene, a main odour constituent of citrus fruits, is added to cleaning products such as hand cleansers to give a lemon-orange fragrance. Which of the following about limonene is correct? A It exhibits cis and trans isomerism. B It reacts with acidified concentrated K2Cr2O7 to give a colourless and odourless gas. C It reacts with H2 in nickel to form an alkane with formula C9H18. D It reacts with Br2 in organic solvent to form a product with 4 chiral carbons. 16 Compound R is heated in a sealed tube with ammonia, whereas compound S is reacted with hydrogen in the presence of catalyst. Both reactions give the same product. Which are the structures of R and S? R S A C6H5Br C 6H5CN B CH3CH(Br)CH3 CH 3CH(CN)CH3 C CH3CH2CH2Br CH 3CH2CN D CH3CH(Br)CH3 CH 3CH2CN 243

© ACJC 2013 9647/01/Prelim/13 [Turn over 9 17 T, U and V are three different 4–carbon compounds. T and U react together to form an ester. V reacts with T to give the same ester but much less readily when compared to U. Which of the following could be T? A butanoic acid B butanone C butan-2-ol D butanoyl chloride 18 Which sequence shows the correct order of decreasing ease of hydrolysis? A CH3CH2COCl > CH3CH2Cl > CH2=CHCl B CH3CH2Cl > CH3CH2Br > CH3CH2I C D 19 2-methylpropan-1-ol can be converted into 2-methylpropan-2-ol in two steps. CH3 CH3 OH CH3 CH3 OH CH3 Step