NYJC_Prelim_CHEM_P3

NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY 9746/03 Paper 3 16 September 2009 2 hours Candidates answer on writing paper Additional Materials: Data Booklet Graph paper READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer 4 out of 5 questions. Write your answers on the writing paper provided Begin each question on a fresh piece of paper. You are advised to show all working and calculations This document consists of 9 printed pages and 1 blank page H2 Chemistry 9746/03/NYJC J2/09PX

2 H2 Chemistry 9746/03/NYJC J2/09PX Turn over 1 Aluminum is an element in Period 3 of the Periodic Table. (a) The graph below shows the second ioniza tion energies of eight elements with consecutive proton number. (i) Which of the above elements, A to H, is Aluminium? Explain your answer. [2] (b) A 0.400g sample of a mineral, AB(CO 3)2 (where A and B are Group II elements) was heated strongly until no further change occurs. A white powder weighing 0.275g was collected and shaken with 200 cm 3 of water. A portion of the white powder remained insoluble and was then filtered. The residue was dri ed and it weighed 0.057g. (i) Assuming that the products on heat ing consist of the oxides of A and B and carbon dioxide, write a balanced equation for the decomposition of AB(CO3)2 [1] (ii) Calculate the mass of carbon dioxide produced. [1] (iii) Hence, or otherwise, identify the metals, A and B , showing your working clearly. [2] (c) Arrange the following molecules in order of increasing boiling points. Explain your choice in term of structure and bonding. NaF, H 2O, MgO, CO 2, CH 3NH2 [5]

3 H2 Chemistry 9746/03/NYJC J2/09PX Turn over d(i) Which of the following amino acid residues is most likely to be found on the outer surface of a water soluble globular protein? Explain your answer. H2NC H C CH2 OH O phe H2NC H C (CH2)4NH2 OH O Lys H2NC H C CH2 OH O OH Ser HN C OH O Pro H2NC H C CH2 OH O CH CH3 CH3 Leu [2] (ii) State the type of R group interactions that would occur between these residues. [1] (iii) The white of an egg is about 88% wate r and 12% protein (by mass). When an egg is heated, the white undergoes obvious changes. Name the process responsible for thes e changes and explain the structural changes which the food components undergo. [3] (iv) Amino acids exist as zwitterions in aqueous solutions. Choose any one