MI Prelim 9647_P3_Answers

Class Adm No Candidate Name: This question paper consists of 11 printed pages and 1 blank page. 2017 Preliminary Examination II Pre-University 3 H2 CHEMISTRY 9647/03 Paper 3 Free Response 15th Sept 2017 2 hours Candidates answer on separate paper. Additional materials: Answer Paper Data Booklet READ THESE INSTRUCTIONS FIRST Do not turn over this question paper until you are told to do so Write your name, class and admission number on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer any four questions. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. You are reminded of the need for good English and clear presentation in your answers. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. Question 1 2 3 4 5 Total Marks 20 20 20 20 20 80

2 1 (a) Graphite is a naturally-occurring form of crystalline carbon and is found in metamorphic and igneous rocks. Graphite is extremely soft and cleaves with very light pressure yet it is extremely resistant to heat and nearly inert in contact with almost any other material. These extreme properties give it a wide range of uses in metallurgy and manufacturing. (i) With reference to the structure, account for the following properties of graphite.  Soft  Heat resistant and inert [3] Graphite has a giant covalent structure (;). The bonding between the layers is weak temporary dipole – induced dipole forces(;) which can be easily overcomed, allowing the layers to slide over each other easily and thus graphite is soft. Large amount of thermal energy is required to break the strong covalent bonds(;) between the carbon atoms within the layers which account for its resistance to heat. (ii) The following table shows some thermochemistry data. Reaction H / kJ mol-1 Standard enthalpy change of atomisation of carbon +715 Enthalpy change of 4H(g) + O(g) + C(g) → CH3OH(l) -2069 With the use of relevant data from the Data Booklet and the above information, calculate the enthalpy change of formation of methanol. [3] ∆Hf = +715 +½(+496) + 2(+436)+(-2069) = -234 kJ mol-1 (b) A butane burner is used to heat the air in a hot air balloon. The hot air balloon has a volume of 2.1 m3 and its volume does not change when the enclosed air is heated. (i) Using the ideal gas equation, calculate the amoun