MJC H1 CHEM P2

No part of this paper should be repro duced for commercial use without the prior written permission of Meridian Junior College. Name : ______________________ Class: ______ Reg Number: _____ Meridian Junior College 2009 JC2 Preliminary Examination H1 Chemistry 8872 14 September 2009 2 hours Paper 2 Candidates to answer Section A on the Question Paper and Section B on separate writing paper. Additional Materials: Data Booklet Writing paper INSTRUCTION TO CANDIDATES Write your name, class and register number in the spaces provided at the top of this page. Section A Examiner’s Use Paper 1 MCQ / 30 Q1 / 7 Q2 / 8 Q3 / 10 Answer all questions. Section B Answer any tw o questions. Paper 2 Section A At the end of the examination, fasten your answers for Section B behind Section A. INFORMATION FOR CANDIDATES Q4 / 15 Q5 / 20 Q6 / 20 The number of marks is given in brackets [ ] at the end of each question or part question. You are reminded of the need for good English Paper 2 Section B and clear pr esentation in your answers. Q7 / 20 Total / 110 This question paper consists of Page 1 to 19. ©chemistry department@meridian jc [Turn over

Section A Answer all the questions in this section in the spaces provided. 1(a) Magnesium bromide, MgBr 2, is a white solid that readily absorbs moisture from the atmosphere. It is often used as a mild sedative. (i) Using magnesium bromide as an exam ple, explain what is meant by the term lattice energy. (ii) Use the energy level diagram, together with the given data to determine the lattice energy of magnesium bromide . Enthalpy change of hydration of magnesium ion, ∆Hhyd( 2+Mg ) -1921 kJ mol-1 Enthalpy change of hydration of bromide ion, ∆Hhyd( -Br ) -336 kJ mol-1 Enthalpy change of solution of magnesium bromide, Hsoln(MgBr2) -186 kJ mol-1 ∆H soln (MgBr2) Mg2+(g) + 2Br-(g) ∆Hhyd( 2+gM ) + 2 x ∆Hhyd( -Br ) ∆Hlatt MgBr2 (s) Mg2+(aq) + 2Br-(aq) ©chemistry department@meridian jc [Turn over 1

(iii) Explain how you would expect the num erical magnitude of the lattice energy of MgBr2 to compare with that of sodium fluoride, NaF. [4] (b) (i) With the aid of an equation, define the first ionisation energy of iodine. (ii) State and explain how you would expect the first ionisation energy of iodine to compare with that of fluorine. [3] [Total : 7] ©chemistry department@meridian jc [Turn over 2

2 Early Periodic Tables, such as that devised by Mendeleev, listed the then known elements in order of their relative atomic mass. (a) When Mendeleev created the table, ther e were uncertainties regarding the relative atomic mass of tellurium. It is now known that there are eight isotopes of tellurium. Complete the followi ng table. Give your answers to four significant figures. isotope percentage abundance isotopic mass x percentage abundance tellurium-120 0.09 11 tellurium-122 2.46 300 tellurium-123 0.87 107 tellurium-124 4.61 572 tellurium-125 6.99 874 tellurium-126 18.71 2357 tellurium-128 31.79 tellurium-130 Hence, calculate the relative atomic mass of tellurium to 1 decimal place. [3] ©chemistry department@meridian jc [Turn over 3

(b) Tellur ium (IV) chloride, TeCl4, is a pale yellow solid at room temperature with a melting point and boiling point of 224°C and 380°C respectively. In the molten state, TeC l4 dissociates into TeCl 3 + and Te 2Cl10 2-. Gaseous tellurium (IV) chloride, TeCl4, has a structure similar to sulphur tetrafluoride, SF4. Explain in terms of structure and bonding, the relative electrical conductivity of TeCl4 in the molten and gaseous state. [2] (c) Tellurium resembles silicon in many aspects. For example, both are metalloids and are used as semiconductors. Tellurium ( IV) oxide, TeO 2, reacts with concentrated strong bases in the same way as silicon ( IV) oxide, SiO2. (i) Write a balanced equation for the reaction between TeO2 and NaOH. (ii) Predict the pH of the solution formed when gaseous tellurium tetrachloride, TeCl 4, is bubbled into water. Suggest an equation for this reaction. pH of solution : …………………………... ......................... Equation: .............. ........................................................... [3] [Total : 8] ©chemistry department@meridian jc [Turn over 4

3 The following shows a series of reactions that compound Z can undergo. B C H (a) Draw the structures of compounds A to F in the boxes provided below. + Step I Step II KMnO4/H+ Heat Cl2, Fe Heat NaOH(aq) heat Ethanolic NaCN, heat Ethanolic NaOH, heat NaOH(aq), heat Cl C H Cl C CH3 OH H K2Cr2O7/H+ Heat A D G H E C F Cl C O O-Na+Cl Cl Cl Cl Cl Compound Z A B ED C F ©chemistry department@meridian jc [Turn over [6] 5

(b) When treated with NaOH in ethanol, compound Z produces a mixture of isomers, G and H. Draw the full structural formulae of G and H. HG [2] (c) State the reagents and conditions required in Steps I and II. Step I Reagents: …………………………. Conditions: ……….……………….. Step II Reagents: ………………………… Conditions: ……………………….. [2] [Total: 10] ©chemistry department@meridian jc [Turn over 6

4 Sulphur compounds occur naturally in petrol. The presence of such compounds gives rise to the emission of toxic oxides of sulphur from car exhausts. One such pollutant produced fr om car emissions is the gas sulphur dioxide, SO2. Sulphur dioxide reacts with water and oxygen in the atmosphere to produce ‘acid rain’, a dilute solution of sulphuric acid, resulting in further damage to urban architecture. One process used to remove sulphur compounds from petroleum and diesel is called “hydroprocessing”. This process uses catalysts consisting of metals deposited as thin layers on porous aluminium supports. Hydroprocessing converts the sulphur compounds in the fuel to the gas hydrogen sulphide, H2S. Some of the hydrogen sulphide produced is oxidised to sulphur dioxide and water as shown in equation 1. 2H2S(g) + 3O2(g) → 2SO2(g) + 2H2O(g) (1) The sulphur dioxide produced is then r eacted with the rema ining hydrogen sulphide to produce solid sulphur as follows. 2H2S(g) + SO2(g) → 3S(s) + 2H2O(l) (2) Sulphur dioxide also dissolves in water to form su lphurous acid, H 2SO3. Unlike sulphuric acid, sulphurous acid is a weak acid and dissociates partially to form hydrogensulphites and protons, as shown in equation 3. H2SO3(aq) H+(aq) + HSO3 –(aq) (3) While sulphuric acid in the environment is harmful, a mixture of hydrogen sulphites and sulphurous acid is widely used in the food industry as an “acidity regulator”. (a) (i) Draw the dot-and-cross diagram as well as the displayed formula showing the shape of a molecule of sulphurous acid. ©chemistry department@meridian jc [Turn over 7

(ii) Using the Valence Shell Electron Pair Rep ulsion Theory, explain the shape around the sulphur atom in a molecule of sulphurous acid. [4] (b) A student titrated a 25.0 cm 3 solution of 0.0125 mol dm-3 potassium hydroxide with 0.010 mol dm -3 sulphurous acid solution. T he reaction occurring in this titration is KOH(aq) + H2SO3(aq) → KHSO3(aq) + H2O(l) A total of 40.0 cm 3 of acid was added. The following graph shows the