CJC H2 Chem 2013 Prelim P1 QP

CHE Paper 1 Addition READ T Write in Do not Write a Answer There a four pos Choose Multiple Read th Each co Any rou Calcula CATH JC2 P Highe EMISTR 1 Multiple C nal Material THESE INS n soft pencil use staples and/or shad r Sheet in th are forty qu ssible answ e the one y e Choice An he instruct orrect answ ugh working ators may be Thi HOLIC JUN PRELIMINA er 2 RY Choice ls: Multip l Data B STRUCTION . s, paper clip e your na m he spaces p uestions in wers, A, B, C ou conside nswer Shee tions on the wer will score g should be e used. s documen NIOR COLL ARY EXAM le Choice A Booklet NS FIRST ps, highlight me, NRIC / provided. this paper. C and D. r correct an et. e Multiple C e one mark done in this t consists o LEGE INATIONS Answer She ters, glue or FIN numb Answer al nd record yo Choice An k. A mark wi s booklet. of 18 printed et r correction er and HT l questions our choice swer Shee ill not be de d pages and fluid. group on t . For each in soft pen t very care educted for a d 0 blank pa 96 3 Septemb the Multipl e question, t ncil on the s efully. a wrong an age. [Tu 647/01 ber 2013 1 hour e Choice here are separate swer. urn over 378

2 9647/01/CJC JC2 Preliminary Exam 2013 For each question there are four possible answers, A , B , C and D. Choose the one you consider to be correct. 1 Sodium carbonate peroxyhydrate with the formula (Na 2CO3)xyH2O2 is used in some eco-friendly cleaning products and as a laboratory source of anhydrous hydrogen peroxide. 2MnO4 – + 6H+ + 5H2O2  2Mn2+ + 8H2O + 5O2 When 20.0 cm 3 of 0.100 mol dm –3 sodium carbonate peroxyhydrate is titrated with 0.200 mol dm–3 acidified KMnO4, it requires 12.0 cm3 of acidified KMnO4 before the first pink colour appears. When an identical sample is acidified, it releases 96.0 cm 3 of carbon dioxide at room conditions. What is the ratio of x:y ? A 1 : 3 B 2 : 3 C 2 : 1 D 3 : 1 2 Use of the Data Booklet is relevant to this question. Species containing one or more unpaired electrons and can be attracted by an external magnetic field are said to be paramagnetic. Which of the following species is not paramagnetic? A Cr 3+ B Cu + C Ni 2+ D V 3+ 3 Elemental oxygen exists in the atmosphere in two forms, O 2 and O 3. Even though O 2 and O3 are both made up of oxygen atoms, they have different physical and chemical properties. Which of the following best explains why O3 is more soluble in water compared to O2? A O 3 is more stable than O2 and thus O3 is able to react more readily with water. B O 3 is able to form more extensive van der Waals’ forces with water molecules as compared to O2. C O 3 is able to form permanent dipole-permanent dipole interaction with water but O2 is not able to do so. D O 3 has more lone electrons than O 2 and therefore forms stronger ion-dipole interaction with water. 379

3 9647/01/CJC JC2 Preliminary Exam 2013 4 The diagram shows a liquid flowing from a burette and a negatively charged rod being brought near the flow. What would happen to the flow of the liquid if the liquid were methanol and carbon tetrachloride respectively? methanol carbon tetrachloride A Deflected towards the rod, larger deflection angle Deflected towards the rod, smaller deflection angle B Deflected towards the rod, smaller deflection angle Deflected towards the rod, larger deflection angle C Not deflected Deflected towards the rod D Deflected towards the rod Not deflected Burette Liquid 380

5 U Th 7 W A B C D Use of the D he second to 19 in the Which of the A L has a B E and C H has D C and 50 100 150 200 250 300 350 400 450 500Second Ionisation Energies / kJ mol-1 9 Data Booklet ionisation e e Periodic T following s a larger ato L– have full higher first K form com 0 0 0 0 0 0 0 0 0 0 0 C 9647/01/CJC t is relevant energies of Table are re statements a mic radius t y filled p-or ionisation e mpounds wit D E 4 JC2 Prelimina t to this que successive presented i about eleme than D. rbitals. energy than th the formu Elem F G ary Exam 201 estion. e elements in the graph ents C to L G. ula KC2 and ents H I 3 with atomic h. is incorrec d KC3. J K c numbers b ct? L between 381

5 9647/01/CJC JC2 Preliminary Exam 2013 6 A simplified structure of a molecule of chlorophyll is shown. Mg is situated in the centre of a planar arrangement of the four N atoms. Which of the following is not true? A The hybridisation about N1 is sp2. B The hybridisation about Mg is sp3. C The bonding between Mg and N2 is ionic. D The bonding between Mg and N1 is dative covalent. 7 The graph below shows how pV changes with p for the three gases, J, K and L , at a fixed temperature (where p = pressure, V = volume). Which of the following correctly identifies the gases? Gas J Gas K Gas L A 1 mol of NH3 1 mol of H 2 1 mol of N 2 B 1 mol of N2 1 mol of H 2 1 mol of NH 3 Gas K 400 200 pV p Gas L Gas J 0 N1 MgN N2 N O 382

6 9647/01/CJC JC2 Preliminary Exam 2013 C 2 mol of N2 1 mol of H 2 1 mol of NH 3 D 2 mol of H2 1 mol of NH 3 1 mol of N 2 8 Solutes dissolve in solvents to form solutions. If a semi-permeable membrane that allows solvent molecules to pass through it, is placed between a pure solvent and a solution containing a solute in that solvent, pure solvent only will go through the membrane into the solution. This process is called osmosis. Which statement regarding ∆S is correct for the following processes? A Dissolving the solute in the solvent results in a negative ∆S. B Evaporation of the solvent from the solution results in a negative ∆S. C Cooling the solution will not change ∆S since the number of particles in the system is unchanged. D Movement of solvent molecules through the semi-permeable membrane during osmosis results in a positive ∆S. 9 The ionic product of water at 10 oC is 2.93 x 10–15 mol2 dm–6. What is the pH of a solution containing 0.02 mol dm–3 of Ba(OH)2 at 10 oC? A 12.6 B 12.9 C 13.1 D 13.3 10 The pH of human blood is constant at about 7.4. Which species present in the human body removes excess H +(aq) to help keep the blood pH constant? A CO 2 B CO 3 2– C HCO 3 – D H 2CO3 11 Use of the Data Booklet is relevant to this question. Hydrazine (N 2H4) can be used to reduce metal ions to their elemental forms in the treatment of wastewater. An important half-equation involving hydrazine is shown. N2 + 4H2O + 4e– ⇌ 4OH– + N2H4 Eo = –1.17 V Which of the following substances cannot be removed from a wastewater source by hydrazine? A Pb 4+ B Fe 3+ C Zn 2+ D V 3+ 383

7 9647/01/CJC JC2 Preliminary Exam 2013 12 The last stage in the production of aluminium involves the electrolysis of refined aluminium oxide (A l2O3) dissolved in molten cryolite (Na 3AlF6) using graphite electrodes. A typical cell operates at 3.0 x 10 5 A. Oxygen gas produced at the anode reacts with graphite forming carbon dioxide gas. The electrodes are replaced when 50 % of the graphite is used up. If the mass of the electrode used is 5000 kg, what is the time taken, in minutes, before replacement of the electrode is necessary? A 1.34 x 10 5 B 2.68 x 10 5 C 4.47 x 10 3 D 8.94 x 10 3 13 One of the reactions that occurs in a sample of polluted air containing oxides of nitrogen is the oxidation of nitrogen monoxide to nitrogen dioxide. 2NO(g) + O2(g)  2NO2(g) The table shows some data obtained in experiments carried out at 25 °C to determine the rate equation for this reaction. Experiment Initial concentration / mol dm–3 Rate of formation of NO2 / mol dm–3 s–1 NO(g) O 2(g) 1 0.025 0.020 8.75 x 10–2 2 0.050 0.020 3.50 x 10–