MJC H1 CHEM P2 QP

1 [Turn Over Name: __________________________ Class: 14_______ Reg Number: _____ MERIDIAN JUNIOR COLLEGE JC2 Preliminary Examination Higher 1 ________________________________________________________________________ Chemistry 8872/02 Paper 2 16 September 2015 2 hours Additional Materials: Data Booklet Writing Papers Graph Paper ________________________________________________________________________ READ THESE INSTRUCTIONS FIRST Write your name, class and register number in the spaces at the top of this page. This booklet contains Section A and Section B. Section A : Pg 2 to 10 Answer all questions in Section A in the spaces provided on the question paper. You are advised to spend about 1 h on Section A. Section B : Pg 11 to 16 Answer 2 out of 3 questions in Section B. You are advised to spend about 1 h on Section B. Hand in Section B separately from Section A. Fasten your answers for Section B behind the given Cover Page . Detach the Cover Page from the last page behind this booklet. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. ________________________________________________________________________ This document consists of 16 printed pages (including this cover page). Examiner’s Use Paper 1 MCQ / 30 / 33 % Paper 2 Section A Q1 / 15 Q2 / 12 Q3 / 13 Paper 2 Section B / 40 Paper 2 Total / 80 / 67 % Grand Total / 100 % Grade

2 [Turn Over Section A: Structured Questions Answer all the questions in this section in the spaces provided. 1 When gaseous phosphorus( V) chloride is heated in a closed container, the follow ing equilibrium is established, producing phosphorus(III) chloride and chlorine. PCl5(g) PCl3(g) + Cl2(g) (a) (i) Draw the dot-and-cross diagram for phosphorus(III) chloride. [1] (ii) Draw a diagram to show the shape of phosphorus(V) chloride. [1] (b) In terms of structure and bonding, e xplain whether phosphorus( V) chloride or phosphorus(III) chloride would have a higher boiling point. [3]

3 [Turn Over (c) (i) Define what is meant by dynamic equilibrium. [1] When 1.0 mol of phosphorus( V) chloride is placed in a 5.0 dm 3 vessel at 500 K, the equilibrium amount of phosphorus(III) chloride is found to be 0.508 mol. PCl5(g) PCl3(g) + Cl2(g) (ii) Write an expression for the equilibrium constant, Kc, for the equilibrium, stating the units. [1] (iii) Calculate the equilibrium constant, Kc, for the reaction. [3]

4 [Turn Over (iv) Explain what would happen to the equilibrium position and rate of reaction when the volume of the reaction vessel is decreased. [3] (v) The equilibrium can be described a s a redox reaction. Explain why, including relevant oxidation numbers in your explanation. [2] [Total: 15]

5 [Turn Over 2 In the third period of the Periodic Table, there is considerable variation of chemical and physical properties from sodium to argon. (a) The graph below shows the first ionisation energy from sodium to argon. (i) Using an equation, define the term first ionisation energy of Al. [1] (ii) Explain why the first ionisation energy across the period generally increases. [2] (iii) Explain the decrease in the first ionisation energy from magnesium to aluminum. [1] first ionisation energy Na Mg Al Si P S Cl Ar

6 [Turn Over (b) (i) On the axes below, sketch a graph to show the pH of the resultant solution s when period 3 chlorides are dissolved in water. [1] (ii) Write equations to show how SiCl4 and PCl5 react with water. [2] pH of chloride. Na Mg Al Si P S

7 [Turn Over (c) The properties of oxides of the elements of the third period depend on the difference in electronegativity values between the element and oxygen. The table below shows the electronegativity of elements of the second and third period as proposed by Linus Pauling. Li 0.98 Be 1.57 B 2.04 C 2.55 N 3.04 O 3.44 F 3.98 Ne − Na 0.92 Mg 1.31 Al 1.61 Si 1.90 P 2.19 S 2.58 Cl 3.16 Ar − (i) Calculate the difference in electronegativity between the element a nd oxygen for the oxides BeO, Al2O3 and SO2. [1] (ii) Hence, use your values in (c)(i) to predict the following prop erties of beryllium oxide, BeO. 1. structure and bonding [1] 2. the acid-base nature [1] (iii) Write equations to describe how aluminum oxide r eacts with aqueous HC l and aqueous NaOH respectively. [2] [Total: 12] BeO Na2O Al2O3 SO2 2.52

8 [Turn Over 3 Alcohols are used as fuels. The first four aliphatic alcohols (methanol, ethanol, propanol and butanol ) are increasingly being used as fuels because they can be synthesi sed chemically or biologically. (a) Butan-1-ol can be synthesised from but-1-ene, represented by the chemical equation below. CH3CH2CH=CH2(g) + H2O(g)  CH3CH2CH2CH2OH(l) (i) Using bond energy values from the Data Booklet, calculate the enthalpy change of the reaction. [3] (ii) The calculated value in (a)(i) differs significantly from literature value. Suggest a reason for the discrepancy between the two values. [1]

9 [Turn Over (b) An experiment was carried out to determine the standard enthalpy change of combustion of butan -1-ol, Δ Hc(butan-1-ol). A quantity of butan -1-ol was burnt underneath a copper can containing 200 g of water. The following results were obtained. Volume of butan-1-ol used = 1.2 cm3 Initial temperature = 27.0 oC Final temperature = 51.5 oC Density of butan-1-ol = 0.810 g cm–3 (i) Given that the process was only 80% efficient, calculate ΔHc(butan-1-ol). Given that the heat capacity of the copper can is negligible and that the specific heat capacity of water is 4.18 J g–1 K–1. [3] (ii) The true value of the standard enthalpy change of combustion of butan -1-ol is –2670 kJ mol –1. Suggest a reason for the discrepancy between the true value and that calculated in (b)(i). [1]

10 [Turn Over (c) The molecular formula of butan -1-ol is C 4H10O. There are three other structural isomers with molecular formula C4H10O. One of the isomers is a secondary alcohol. Describe how the secondary alcohol could be distinguished by a simple chemical test from butan-1-ol. [2] (d) Outline how the following conversion could be carried out from butan-1-ol. [3] [Total: 13]