2017 MGS Prelim P2

Page 2 of 24 Methodist Girls’ School Chemistry Paper 2 Sec 4 Preliminary Examination 2017 Section A (70 marks) Answer all the questions in this section in the spaces provided. A1 Carbon is an element with chemical symbol C and atomic number 6. Many substances are made from carbon atoms. (a) Graphene is a new 2-dimensional material made of carbon a toms. Graphene can be described as a ‘one-atom-thick’ layer of graphite. Using your understanding of bonding and structure, predict which of these statements would be true and which would be false. true false Graphene is slippery. Graphene is soluble in organic solvent. Graphene conducts in solid state. Graphene is a gas at room temperature. [2] (b) Carbon disulfide, CS 2, is a compound of carbon used in the m anufacture of fibres and polymers. Draw a ‘dot-and-cross’ diagram using the outer electrons to show the bonding in carbon disulfide. [2]

Page 3 of 24 Methodist Girls’ School Chemistry Paper 2 Sec 4 Preliminary Examination 2017 A2 Ethane reacts with chlorine in the presence of sunlight. The equation for this reaction is: Some bond energies are given in the table. Bond Bond energy in kJ per mole C−C 607 C−H 413 C−Cl 327 Cl−Cl 243 H−Cl 432 (a) Show that the enthalpy change, ΔH, for this reaction is −103 kJ. [2] (b) Draw a labelled energy profile diagram for the reaction of ethane with chlorine, including activation energy and enthalpy change. [2] Energy Progress of reaction

Page 4 of 24 Methodist Girls’ School Chemistry Paper 2 Sec 4 Preliminary Examination 2017 A3 0.03 g of magnesium ribbon reacted with excess dilute hydrochloric acid at room temperature. The volume of gas produced was recorded every 20 seconds. Mg + 2HCl → MgCl2 + H2 The results obtained in the experiment, using 0.03 g of magnesium ribbon and excess dilute hydrochloric acid, are shown as line C on the graph, shown. The experiment was repeated under different conditions and the results obtained plotted as lines A, B, D and E on the graph. (a) State which line, A, B, D or E, was obtained when 0.03 g of magnesium ribbon reacted with excess dilute hydrochloric acid at a temperature below room temperature. [1]

Page 5 of 24 Methodist Girls’ School Chemistry Paper 2 Sec 4 Preliminary Examination 2017 (b) State which line, A, B, D or E, was obtained when 0.015 g of magnesium ribbon reacted with excess dilute hydrochloric acid at room temperature. [1] (c) (i) State which line, A, B, D or E, was obtained when 0.03 g of magnesium ribbon were replaced by 0.03 g of magnesium powder. [1] (ii) Explain your answer based on the shape of the line chosen in comparison to line C. [1] (d) State an d explain, in t