ACJC_H2_CHEM_P1 Prelim

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 The hardness present in a water sample due to dissolved calcium ions can be determined by using ion-exchange column as shown in the diagram. Ca2+ + 2H+-resin → Ca2+-resin + 2H+ A 50 cm 3 sample of a solution containing calcium sulfate was passed through the ion- exchange resin. The calcium ions in the sample were quantitatively exchanged by hydrogen ions. The sample collected in the flask required 25 cm 3 of 1.0 × 10 -2 mol dm-3 potassium hydroxide for complete neutralisation. What was the concentration of the calcium sulfate in the original sample? A 2.5 × 10 -3 mol dm-3 B 5.0 × 10-3 mol dm-3 C 2.0 × 10-2 mol dm-3 D 4.0 × 10-2 mol dm-3 Hard water Ion-exchange resin Treated water 2 A tube filled with 50 cm 3 of methane and 150 cm 3 of oxygen at room temperature was inverted over a vessel containing KOH (aq) as shown in the diagram. The hydrocarbon was ignited for the following reaction to take place. CH 4 + 2O2 → CO2 + 2H2O When the setup is cooled to room temperature, at which level will the liquid be? A. 50 cm3 B. 100 cm3 C. 150 cm3 D. 200 cm3 ACJC 2011 9647/01/Aug/2011 [Turn over

3 3 The successive ionisation energies (IE) of two elements, A and B, are given below: IE/ kJ mol-1 1 st 2 nd 3 rd 4 th 5 th 6 th 7 th 8 th A 550 1065 4138 5500 6910 8760 10230 11800 B 1140 2103 3470 4560 5760 8550 9940 18600 What is the likely formula of the compound that is formed when A reacts with B? A AB2 B AB C A2B D A2B3 4 The value of pV is plotted against p at the same temperature for four gases, where p is the pressure and V is the volume of the gas. Which of the following represent the possible identities of Gases 1 to 4? Gas 1 Gas 2 Gas 3 Gas 4 A Ne CH 3F HF H2O B Ne HF CH3F H 2O C H2O Ne CH3F HF D H2O HF CH3F Ne Gas 1 Gas 4 Gas 2 Gas 3 pV p 5 In which of the following sequences are the molecules quoted in order of decreasing boiling points? A Ti, K, Ca B I2, HF, HCl C SCl2, AlCl3, MgCl2 D CCl4, CH4, CH2Cl2 ACJC 2011 9647/01/Aug/2011 Preliminary Examination

4 6 When two liquids are mixed, heat may be evolved if the intermolecular bonds formed are stronger than those broken, even if there is no chemical reaction occurring. Which of the following pair of liquids, when mixed, will give out heat? A CHCl 3 and C5H12 B CCl4 and (CH3)2CO C CCl4 and CH3CH2OH D CH2Cl2 and (CH3)2CO 7 The following graph shows the first ionisation energies of eight consecutive elements J to R, which have atomic numbers between 3 to 20 in the Periodic Table. M R Q P N J K L Atomic Number 1st Ionisation Energy/ kJ mol-1 Which one of the following statements about the elements is false? A O