NYGH 2018-S3EOY-IP Chem P2

Class Register Number Name NANYANG GIRLS’ HIGH SCHOOL End-of-Year Examination 2018 Secondary Three CHEMISTRY Paper 2 Theory Paper 1 hour 45 minutes Monday 8 October 2018 1000 - 1145 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 B5, B6 and B7 Either or B7 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 B7 Either (for Either) or B7 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 B5 / 9 B6 / 11 B7 Either / B7 Or / 10 Total / 100 Setters: CJS / NHK This document consists of 15 printed pages and 1 blank page. NANYANG GIRLS’ HIGH SCHOOL [Turn over]

2018 End-of-Year Examination Secondary Three 2 Nanyang Girls’ High School Setters: CJS/ NHK Chemistry Section A (40 marks) Answer all questions. Write your answers in the spaces provided. A1 The structures of ethanoic acid and sodium ethanoate are given below. ethanoic acid sodium ethanoate (a) State the number of sigma bonds (σ bonds) and the number of pi bonds (π bonds) present in a single molecule of ethanoic acid. number of sigma bonds ……………………………………………………………… [1] number of pi bonds …………………………………………………………………… (b) Study the structure of ethanoic acid. (i) State the geometry of the bonds around the carbon atom that has been labelled with an asterisk (*). [1] …………………………………………………………………………………… (ii) Explain your answer in (bi) with reference to the number of bonding pairs and non-bonding pairs (lone pairs) of electrons in the valence shell of the carbon atom. [1] …………………………………………………………………………………… …………………………………………………………………………………… (c) Briefly explain why ethanoic acid and sodium ethanoate can both conduct electricity when dissolved in water. [1] …………………………………………………………………………………………... …………………………………………………………………………………………...

2018 End-of-Year Examination Secondary Three 3 Nanyang Girls’ High School Setters: CJS/ NHK Chemistry [Turn Over] (d) The melting point of ethanoic acid is 16.6°C, while the melting point of sodium ethanoate is 324°C. Explain why the melting point of sodium ethanoate is significantly higher than the melting point of ethanoic acid. [2] …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... (e) (i) Sodium ethanoate is a salt of ethanoic acid. Name the method that sodium ethanoate can be prepared from dilute ethanoic acid and aqueous sodium hydroxide. [1] …………………………………………………………………………………… (ii) Another salt of ethanoic acid is calcium ethanoate Ca(CH3COO)2. Calcium ethanoate is a water soluble salt that is used in both medicine and the food industry. Calcium ethanoate may be prepared in the laboratory by reacting calcium carbonate with dilute ethanoic acid. Briefly describe how an aqueous solution of calcium ethanoate can be prepared from calcium carbonate and dilute ethanoic acid. [2] …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………………

2018 End-of-Year Examination Secondary Three 4 Nanyang Girls’ High School Setters: CJS/ NHK Chemistry (iii) The graph below shows how the solubilities of calcium nitrite, Ca(NO2)2, calcium chloride, CaCl2, and calcium ethanoate, Ca(CH3COO)2, change with temperature. With reference to the graph, explain why it is not possible to crystallise calcium ethanoate from a hot saturated solution of the salt. Hence, state how solid calcium ethanoate should be obtained from aqueous solution. [3] …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… Total [12] Temperature/ oC Solubility/ g of solute per 100 cm3 of water Ca(NO2)2 CaCl2 Ca(CH3COO)2

2018 End-of-Year Examination Secondary Three 5 Nanyang Girls’ High School Setters: CJS/ NHK Chemistry [Turn Over] A2 Study the reaction scheme given below. (a) Identify chemicals A to G, shown in the reaction scheme above. [7] A ………………………… B ………………………… C ………………………… D ………………………… E ………………………… F ………………………… G ………………………… (b) Explain why gas F turns damp red litmus paper blue. [1] …………………………………………………………………………………………... (c) Write an ionic equation for the formation of white precipitate G. [1] …………………………………………………………………………………………... Total [9]

2018 End-of-Year Examination Secondary Three 6 Nanyang Girls’ High School Setters: CJS/ NHK Chemistry A3 45.0 cm3 of 1.60 mol dm–3 aqueous sodium carbonate reacted with 40.0 cm3 of 2.00 mol dm–3 aqueous silver nitrate according to Equation 1. Equation 1: Na2CO3(aq) + 2AgNO3(aq) → Ag2CO3(s) + 2NaNO3(aq) (a) By showing relevant calculations, identify the limiting reagent for the reaction. [3] (b) Calculate the mass, in grams, of silver carbonate produced by the reaction. [2] (c) The silver carbonate was filtered from the mixture, washed and dried. One quarter of the resulting solid was reacted with excess methanol, CH2O, according to Equation 2. Equation 2: Ag2CO3(s) + CH2O(aq) → 2Ag(s) + 2CO2(g) + H2(g) Calculate the total volume, in cm3, of gaseous products formed by the reaction at room temperature and pressure. [4]

2018 End-of-Year Examination Secondary Three 7 Nanyang Girls’ High School Setters: CJS/ NHK Chemistry [Turn Over] (d) Yii Wenn set up the experiment shown below to investigate the rate of diffusion of the gaseous products, carbon dioxide and hydrogen. Yii Wenn observed that the level of the water at point Z moved down. Briefly explain her observation. [3] …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... Total [12]

2018 End-of-Year Examination Secondary Three 8 Nanyang Girls’ High School Setters: CJS/ NHK Chemistry A4 Hydrogen peroxide decomposes to form oxygen gas and water according to the chemical equation below. 2H2O2(l) → 2H2O(l) + O2(g) The rate of this reaction can be increased by adding a suitable catalyst, such as aqueous potassium iodide. A student added three drops of aqueous potassium iodide to 50.0 cm3 of 0.108 mol dm–3 hydrogen peroxide at room temperature and pressure. She measured the volume of oxygen gas produced against time. Figure 4.1 shows a graph of her results. (a) Describe how a catalyst increases the rate of reaction. [1] …………………………………………………………………………………………... (b) Using collision theory, explain why the rate of the reaction decreases as the reaction progresses. [2] …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... Figure 4.1

2018 End-of-Yea