NJC_H2_CHEM_P3_Question_Paper Prelim

1 [Turn Over NATIONAL JUNIOR COLLEGE PRELIMINARY EXAMINATIONS Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 3 Free response 9647/03 Wed 17 Sep 2014 2 hours READ THESE INSTRUCTIONS FIRST Answer any four questions. Start your answer to each question on a fresh piece of paper. A Data Booklet is provided. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely behind the cover page. This paper consists of 11 printed pages and 1 cover page.

2 [Turn Over 1 Iodine monochloride, ICl, is an interhalogen compound that is formed when chlorine gas is passed through iodine crystals. Generally, interhalogen compounds have chemical properties similar to that of halogens. (a) (i) Predict the physical state of ICl at room temperature. (ii) By considering the partial charges in ICl, explain how water reacts with ICl. (iii) Hence construct an equation for the reaction of ICl with water. [3] (b) Methylbenzene reacts with ICl in the presence of FeCl3 to form compound A. (i) Draw the structure of A. (ii) Describe the mechanism of this reaction, clearly indicating the role of FeCl3. [4] (c) FeCl3 and FeF3 are both formed from a metal and a non-metal. However, in molten state, only FeF3 is able to conduct electricity and FeCl3 does not. (i) Suggest the structures of FeC l3 and FeF 3 and explain why iron forms two different types of compounds when reacted with the different halogens – fluorine and chlorine. (ii) Using the information given below as well as relevant data from the Data Booklet, construct an energy level diagram for the formation of FeF 3 from its elements to determine its lattice energy. enthalpy change of atomisation of Fe +340 kJ mol –1 first electron affinity of F –328 kJ mol –1 standard enthalpy change of formation of FeF3 –989 kJ mol –1 [7] Suggest an equation for the f C

3 [Turn Over (d) Iron is a transition metal, a d-block element that varies from s-block metals in terms of physical properties. The table below gives data about some physical properties of the elements – iron and calcium. property calcium iron relative atomic mass 40.1 55.8 atomic radius/ nm 0.197 0.126 density/ g cm–3 1.54 7.86 electrical conductivity Good Good (i) Write down the full electronic configurations of calcium and iron. (ii) Explain why the atomic radius of iron is smaller than that of calcium. (iii) Suggest why iron has a higher density than calcium. (iv) Explain which of the 2 metals would be expected to have a higher electrical conductivity. [6] [Total:20]

4 [Turn Over 2 (a) In the qualitative