NYJC H2 Chem Prelim P3 QP

1 NYJC 2017 H2 Chemistry 9729/03 PRELIM [Turn over NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY 9729/03 Paper 3 Free Response 19 SEP 2017 2 hours Candidates answer Section A on the Question Paper Candidates answer on separate paper. Additional Materials: Answer Paper Data Booklet 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 correcti on fluid. Section A Answer all questions . Section B Answer one question 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 to gether. The number of marks is given in brackets [ ] at the end of ea ch question or part question. 1 2 3 4 5 This document consists of 13 printed pages. KiasuExamPaper.com

2 NYJC 2017 H2 Chemistry 9729/03 PRELIM Section A Answer all the questions in this section. 1 (a) (i) Suggest why the melting point of MgO, A l 2 O 3 and SO 3 is decreasing in the following order MgO > A l 2 O 3 > SO 3 [2] (ii) Explain how the electronegativity of the elements in the oxides determine the type of bonding and hence the acid-base nature in MgO and P 4 O 10 .[ 2 ] (b) A student was given 3 unknown oxides A, B and C containing Na 2 O, Al 2 O 3 , and P 4 O 10 , The labels A to C do not correspond to the identities of the o xides. He was given 2 packets of sample mixture, each containing diffe rent mole ratios of oxides A to C given in the table. The student dissolved each sample mixture in half a beaker of w ater and recorded the observations of the resulting solution. Sample A B C Observation of resulting solution 1 1 1 7 Neutral solution 2 1 1 1 Highly acidic solution (i) Write a balanced equation when NaOH reacts with x A l 2 O 3 x P 4 O 10 [2] (ii) By considering the reactions of the oxides with water and the stoichiometric ratios obtained in (i) , account for the observations for s amples 1 and 2. Hence deduce the identities of A, B and C. [4] (c) The mineral dolomite is a double carbonate of magnesium and cal cium, with the formula of CaMg(CO 3 ) 2 . When a sample of impure dolomite was heated at 315 o C, x cm 3 of gas was collected which gave white ppt with lime water. When another sample of the same mass was heated at 530 o C, 2 x cm 3 of gas was collected. When 1.000g of dolomite was reac