NYGH 2017-S3EOY-IP Chem P2

Class Register Number Name NANYANG GIRLS’ HIGH SCHOOL End-of-Year Examination 2017 Secondary Three CHEMISTRY Paper 2 Theory Paper 1 hour 45 minutes Wednesday 4 October 2017 1045 - 1230 Additional materials: Writing paper READ THESE INSTRUCTIONS FIRST Do not open this booklet until you are told to do so. Write your name, register number and class in the spaces at the top of this page and on any separate answer paper used. Section A (40 marks) Answer all questions. Write your answers in the spaces provided on the question paper. Section B (30 marks) Answer all questions including questions B8, B9 and B10 Either or B10 Or. Write your answers on the separate writing paper provided. At the end of the examination, 1. Fasten all your work securely together; 2. Circle B10 Either (for Either) or B10 Or (for Or) in the grid on the right to indicate the question you have answered; 3. Hand in Section A and Section B separately. INFORMATION FOR CANDIDATES The intended number of marks is given in the brackets [ ] at the end of each question or part question. You are advised to spend no longer than 60 minutes on Section A and no longer than 45 minutes on Section B. The use of approved scientific calculators is allowed. A copy of the periodic table is found on page 15. Paper 1 / 30 Paper 2 Section A / 40 B8 / 10 B9 / 10 B10 Either / B10 Or / 10 Total / 100 Setters: CDT / CWJ This document consists of 15 printed pages and 1 blank page. NANYANG GIRLS’ HIGH SCHOOL [Turn over]

2017 End-of-Year Examination Secondary Three 2 Nanyang Girls’ High School Setters: CDT/CWJ Chemistry Section A (40 marks) Answer all questions. Write your answers in the spaces provided. A1 A colourless liquid was left on a chemistry laboratory table. Arthur collected the colourless liquid and conducted a few tests on it. (a) He collected a drop of the colourless liquid and used paper chromatography with water as the solvent. He obtained the following chromatogram with 3 spots, with the help of a locating agent. Suggest what can be deduced about the solubility of the three spots in water. [1] (b) Arthur then heated a sample of the colourless liquid until it completely boiled, while measuring its temperature. Suggest and explain what he would observe in the readings obtained. [2] Total [3] spot A spot B spot C

2017 End-of-Year Examination Secondary Three 3 Nanyang Girls’ High School Setters: CDT/CWJ Chemistry [Turn Over] A2 Calcium and sulfur are two elements in the Periodic Table. (a) State the number of protons and valence electrons of a sulfur atom. [2] number of protons number of valence electrons (b) The two elements react to form calcium sulfide. (i) Draw a Lewis diagram to show the bonding in calcium sulfide. [1] (ii) Explain if you would expect calcium sulfide to conduct electricity at room temperature, referring to its bonding and structure. [2] Total [5]

2017 End-of-Year Examination Secondary Three 4 Nanyang Girls’ High School Setters: CDT/CWJ Chemistry A3 Arsenic acid, H3AsO4, is a tribasic acid. The table below shows the concentration of H+ ions in solutions of different pH. pH concentration of H+ / mol dm-3 1 0.1 2 0.01 3 0.001 4 0.0001 5 0.00001 6 0.000001 7 0.0000001 8 0.00000001 0.0005 mol dm-3 of arsenic acid was found to have a pH of 3. Using the information in the table, explain if arsenic acid is a weak or strong acid. Show all necessary working. [3] Total [3] A4 Sucrose is a carbohydrate that is found in cane sugar. (a) Sucrose contains the elements carbon, hydrogen and oxygen. In order to determine the ratio of the elements, 1 mole of sucrose was combusted with 12 moles of oxygen. It was found that 12 moles of carbon dioxide and 11 moles of water vapour were produced. (i) Name a suitable apparatus for measuring the volumes of carbon dioxide and water vapour produced. [1] (ii) Using the information above, state the molecular formula of sucrose. [1]

2017 End-of-Year Examination Secondary Three 5 Nanyang Girls’ High School Setters: CDT/CWJ Chemistry [Turn Over] (iii) The empirical formula method could also be employed to find the ratio of the elements in sucrose. Given that a sample of sucrose has 41.5% of carbon, 6.40% of hydrogen and 52.1% of oxygen by mass, find its empirical formula. [2] (iv) With reference to your answers in (a)(ii) and (a)(iii), suggest a limitation of using the empirical formula method to find the ratio of the elements in sucrose. [1] (b) Raw sugar is a mixture of sucrose, inorganic ash and other organic matter that includes amino acids, gums and colour impurities obtained during extraction from sugar cane. The flowchart below shows the main steps in the refining of raw sugar. 1 The raw sugar is mixed with saturated syrup. Impurities dissolve in the syrup and are removed, while sugar crystals are obtained. à 2 Sugar crystals are redissolved. Amino acids, gums and colour impurities remain as a precipitate. à 3 Solid activated charcoal is added to the mixture. The inorganic ash sticks to it. Suggest method(s) of separating: (i) amino acids, gums and colour impurities from dissolved sugar crystals in step 2; and [1] (ii) dissolved sugar from its solution after step 3 has been completed. [1] Total [7]

2017 End-of-Year Examination Secondary Three 6 Nanyang Girls’ High School Setters: CDT/CWJ Chemistry A5 Arsenic contamination of groundwater is a problem that affects millions of people across the world. (a) Using spdf notation, state the electronic configuration of an arsenic atom. [1] (b) A sample of arsenic has 2 stable isotopes identified in it, 75As and 73As. (i) Describe a difference between the two isotopes. [1] (ii) Using information from the Periodic Table, calculate the percentage of the 73As isotope present. [2] (c) Arsenic sublimes at 614°C and at atmospheric pressure. Describe and explain the changes in arrangement and movement of arsenic molecules during the sublimation process. [3]

2017 End-of-Year Examination Secondary Three 7 Nanyang Girls’ High School Setters: CDT/CWJ Chemistry [Turn Over] (d) Arsenic is in group 15 of the periodic table, which contains non-metals like nitrogen and metals like bismuth. Suggest why the metallic character of the elements increases down group 15. [1] Total [8] A6 Some tests were carried on a mixture of two solutions that contained 2 cations and 1 anion. The flowchart below shows the tests conducted on the mixture. (a) Identify precipitate W and gas Y. [2] precipitate W gas Y (b) State the formulae of the 2 ions in solution X that came from the original mixture. [2]

2017 End-of-Year Examination Secondary Three 8 Nanyang Girls’ High School Setters: CDT/CWJ Chemistry (c) Identify solid Z and write a chemical equation, with state symbols, for its formation. [2] (d) State another reagent(s) that could have been added to solution X to identify the anion present and the expected observation(s). [1] (e) Acidified barium nitrate was added to another unknown solution and a white precipitate was observed. When acidified calcium nitrate was added to the same solution, there was no precipitate formed. Suggest a possible reason for this observation. [1] Total [8] A7 Transition metal compounds are commonly used in paints. (a) State what is meant by the term “compound”. [1] (b) Suggest why transition metal compounds are suitable used in paints. [1] (c) “Chrome yellow” contains the compoun