NYGH 2016-S3EOY-IP Chem P2

Class Register Number Name NANYANG GIRLS’ HIGH SCHOOL End-of-Year Examination 2016 Secondary Three CHEMISTRY 1 hour 45 minutes Paper 2 Theory Paper 1015 – 1200 hrs Wednesday 5 October 2016 Additional materials: Writing papers 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 7, 8 and 9 Either or 9 Or. Write your answers on the separate writing paper provided. At the end of the examination, 1. fasten all your answers to Section B securely together; 2. tick 9 Either (for Either) or 9 Or (for Or) in the grid below to indicate which 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 one hour on Section A and no longer than 45 minutes on Section B. The use of scientific calculators is allowed. A copy of the periodic table is found on page 13. Examiner’s Use Section A Section B 7 8 9 Either 9 Or Total Setters: SCheong, LSM This document consists of 13 printed pages and 1 blank page. NANYANG GIRLS’ HIGH SCHOOL [Turn over]

2016 End-of-Year Examination Secondary Three 2 Nanyang Girls’ High School Setters: SCheong, LSM Chemistry [Turn Over] A1 Mosquitoes are attracted to humans due to the chemicals we release. Two main chemicals they respond to are carbon dioxide and ammonia. Using the following transparent setup, James carried out an experiment to find out if mosquitoes are more attracted to carbon dioxide or ammonia. Through chemical reactions, carbon dioxide was produced in A and ammonia in B. When the reactions are completed, he removed all removable covers simultaneously to release the gases and mosquitoes. He monitored the direction of mosquito travel. More mosquitoes flew to B than to A, leading James to conclude that mosquitoes are more attracted to ammonia. (a) Write the chemical formula of a substance that James could add to hydrochloric acid in A to produce carbon dioxide and to potassium hydroxide in B to produce ammonia gas. [2] A: B: Section A Answer all questions. Write your answers in the spaces provided. Legend  direction of mosquito travel removable cover

2016 End-of-Year Examination Secondary Three 3 Nanyang Girls’ High School Setters: SCheong, LSM Chemistry [Turn Over] (b) How would James know that the reaction in A had completed? Suggest an observation. [1] (c) James’ teacher did not agree with his conclusion. She argued that more mosquitoes are attracted to B because they detected ammonia faster than they detected carbon dioxide. Using simple calculations, justify the teacher’s argument. [2] Total [5] A2 The table below shows the melting points of some oxides and chlorides of elements in Period 3 of the Periodic Table. group I II III IV V VI oxide Na2O MgO Al2O3 SiO2 P4O6 SO2 melting point / oC 920 2852 2072 1610 24 -73 chloride NaCl MgCl2 AlCl3 SiCl4 PCl5 SCl2 melting point / oC 801 701 178 -70 162 -121 (a) Describe the trend in the melting points of the oxides based on the data given in the table. [1]

2016 End-of-Year Examination Secondary Three 4 Nanyang Girls’ High School Setters: SCheong, LSM Chemistry [Turn Over] (b) Explain, in terms of bonding and structure, (i) the difference between the melting point of SiO2 and P4O6, [2] (ii) the similarity in melting point of NaCl and MgCl2. [1] (c) Predict the melting point of Cl2O. [1] Total [5] A3 The ‘Odda process’ was a method for the industrial production of nitrogen fertilisers invented by Erling Johnson around 1927. The process includes the following steps: Step 1: Phosphate rock, Ca3(PO4)2, is reacted with nitric acid to produce phosphoric acid, H3PO4, and calcium nitrate. Step 2: Cooling the resulting mixture to below 0oC where calcium nitrate crystallises and is separated from phosphoric acid. Step 3: Using carbon dioxide, ammonia and water, crystals of calcium nitrate are converted into aqueous ammonium nitrate and calcium carbonate. CO2 + 2NH3 + H2O + Ca(NO3)2  2NH4NO3 + CaCO3 (a) (i) Write a balanced chemical equation, with state symbols to illustrate the reaction in Step 1. [1]

2016 End-of-Year Examination Secondary Three 5 Nanyang Girls’ High School Setters: SCheong, LSM Chemistry [Turn Over] (ii) When Step 1 was carried out in the presence of Universal Indicator, there was a change in colour from red to orange. Based on the information provided, comment on the relative strengths and the extent of dissociation of phosphoric acid and nitric acid in water. [2] (b) (i) 246 tonnes of calcium nitrate was used in Step 3. Calculate the maximum mass, in tonnes, of ammonium nitrate that can be produced. [1 tonne = 1000 kg] [3] (ii) Calculate the percentage yield if the actual mass of ammonium nitrate produced was 181 tonnes. [1] Total: [7]

2016 End-of-Year Examination Secondary Three 6 Nanyang Girls’ High School Setters: SCheong, LSM Chemistry [Turn Over] A4 Boron is a non -metallic element found in Group III of the Periodic Table. It can be extracted from its oxide (B2O3) by heating with excess powdered magnesium in the absence of air. B2O3 (s) + 3 Mg (s) → 2 B (s) + 3 MgO (s) (a) After the reaction, boron is obtained from the reaction mixture by the following steps: 1. Wash with warm dilute hydrochloric acid; 2. Wash with a solution of sodium hydroxide; 3. Wash with distilled water. Give a reason for each step. [3] Step 1: Step 2: Step 3: (b) Describe how you would determine the purity of the boron extracted. [1] (c) Determine the mass of magnesium that was used if 22kg of boron was extracted. [3] Total [7]

2016 End-of-Year Examination Secondary Three 7 Nanyang Girls’ High School Setters: SCheong, LSM Chemistry [Turn Over] A5 The flowchart below shows a series of chemical reactions. (a) Name the following compounds. [6] A: D: B: E: C: F: (b) Describe what is observed when an excess of sodium hydroxide is added to white precipitate E. [1] (c) Name the products formed when white precipitate F is heated. [1] Total [8] white precipitate F white powder A gas B yellow solid C colourless solution D white precipitate E Yellow preciptate (PbI2) heat + aqueous calcium hydroxide nitric acid nitric acid aqueous potassium iodide aqueous sodium hydroxide

2016 End-of-Year Examination Secondary Three 8 Nanyang Girls’ High School Setters: SCheong, LSM Chemistry [Turn Over] A6 Lumps of magnesium carbonate, of identical shapes and sizes, were treated with 100 cm3 of dilute acid of various concentrations. The volume of carbon dioxide gas evolved after 4 minutes was measured while temperature rise was simultaneously monitored. All other conditions remain the same. The results of the four experiments we