MI Prelim P2 QP

Class Adm No Candidate Name: This question paper consists of 20 printed pages and 2 blank pages. 2018 Preliminary Exams Pre-University 3 H2 CHEMISTRY 9729/02 Paper 2 Structured Questions 12th Sept 2018 2 hours Candidates answer on the Question paper. Additional materials: 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 all questions. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. 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 15 12 12 16 75

2 Answer all the questions in the spaces provided. 1 Ruthenium, Ru, is a Period 5 d-block element. Its ions have the ability to form complexes with both organic and inorganic ligands. One such organic ligand is 2,2-bipyridine which can be represented by bpy. For Examiners’ Use (a) Define the term ligand and suggest why bpy can act as a bidentate ligand. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………[2] (b) In an experiment, varying volumes of solutions of 0.1 mol dm -3 Ru 2+ and 0.1 mol dm-3 bpy are mixed to produce a coloured complex. xRu2+ + ybpy → [Rux(bpy)y]2+ The concentration of the coloured complex formed is proportional to the absorbance of the solution which is measured using a colorimeter. Fig 1.1 shows the results experiment. Fig 1.1 0 10 20 30 40 50 Absorbance Vol of Ru 2+ 3 50 40 30 20 10 Vol of bpy

3 [Turn Over By drawing two best-fit lines in Fig 1.1, deduce the formula of the complex ion formed between Ru2+ and bpy and hence draw the structure of the complex ion. Formula of complex ion: ………………………….. Structure of complex ion: [3] For Examiners’ Use

4 (c) The table below shows the colour of the radiation of the electromagnetic spectrum and the corresponding wavelength range. Wavelength range (nm) Colour Complementary colour 400 – 450 violet yellow 450 – 490 blue orange 490 – 550 green red 550 – 580 yellow violet 580 – 650 orange blue 650 – 700 red green The diagram below shows the UV-Visible spectrum of the complex formed between Ru 2+ and bpy.