CJC H2 Chem 2013 Prelim P1 QP

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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