NYGH 2015-S3EOY-IP Chem P2

Class Register Number Name 南洋女子中学校 NANYANG GIRLS’ HIGH SCHOOL End-of-Year Examination 2015 Secondary Three CHEMISTRY 1 hour 45 minutes Paper 2 Theory Paper 0930 – 1115 hrs Wednesday 7 October 2015 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 12. Examiner’s Use Section A Section B 7 8 9 Either 9 Or Total Setters: CHG, NHK This document consists of 12 printed pages. NANYANG GIRLS’ HIGH SCHOOL [Turn over]

2015 End-of-Year Examination Secondary Three 2 Nanyang Girls’ High School Setters: CHG, NHK Chemistry [Turn Over] Section A Answer all questions. Write your answers in the spaces provided. A1 In an experiment, two gas jars were set up as shown below. (a) State the observation when the glass disc was removed. [1] (b) What difference would you observe if the experiment is repeated using nitrogen dioxide gas instead of bromine gas? [1] (c) Pure bromine exists as a liquid and boils at 58.8oC. A small sample of liquid bromine was heated slowly and its temperature was monitored. State how one can tell whether the sample of bromine was impure. [2] Total [4] air glass disc bromine gas

2015 End-of-Year Examination Secondary Three 3 Nanyang Girls’ High School Setters: CHG, NHK Chemistry [Turn Over] A2 Brine is an impure solution of sodium chloride. The main impurity in brine is calcium chloride. It is removed by reacting brine with sodium carbonate. CaCl2 (aq) + Na2CO3(aq)  CaCO3(s) +2NaCl(aq) (a) State the type of reaction shown. [1] (b) Construct an ionic equation for the above reaction. [1] (c) Suggest how the calcium carbonate is removed from the mixture. [1] Total [3] A3 Sodium nitride (Na 3N) is a solid with a melting point which is above 1000 oC. When sodium nitride is added to excess dilute hydrochloric acid, a violent reaction takes place, producing a solution which contains 2 salts. When the solution is boiled with aqueous sodium hydroxide, a pungent gas is evolved which turns moist red litmus blue. (a) State the type of bonding present in the compound. [1] (b) Describe the bonding and structure in solid sodium nitride. [2] (c) State a physical property of sodium nitride other than its high melting point and boiling point. [1] (d) State the nature of hydrochloric acid in terms of strength and basicity. [2]

2015 End-of-Year Examination Secondary Three 4 Nanyang Girls’ High School Setters: CHG, NHK Chemistry [Turn Over] (e) Construct a chemical equation with state symbols for the reaction between sodium nitride and hydrochloric acid. [2] Total [8] A4 0.400 g of magnesium carbonate is completely dissolved in 100 cm 3 of sulfuric acid. 25.0 cm3 of the resultant solution is pipetted into a conical flask and titrated with 20.50 cm3 of 0.400 g dm−3 aqueous sodium hydroxide. (a) State a suitable indicator for the titration described above. [1] (b) Sulfuric acid is a strong acid. Define the term ‘strong’. [1] (c) Construct chemical equations, with state symbols, for the two reactions described above. [2] (d) Calculate the number of moles of sulfuric acid used in the titration with aqueous sodium hydroxide. [3]

2015 End-of-Year Examination Secondary Three 5 Nanyang Girls’ High School Setters: CHG, NHK Chemistry [Turn Over] (e) Calculate the number of moles of sulfuric acid that reacted with the magnesium carbonate. [2] (f) Hence, calculate the concentration of the sulfuric acid used in the reaction with magnesium carbonate. [2] (g) Suggest a method and suitable reagents for preparing a pure and dry sample of magnesium carbonate. [2] Total [13]

2015 End-of-Year Examination Secondary Three 6 Nanyang Girls’ High School Setters: CHG, NHK Chemistry [Turn Over] A5 Study the flow chart given and answer the questions that follow. (a) Identify the white precipitates, B and C. [2] (b) Write the ionic equation for the formation of gas D. [1] (c) Identify the two ionic compounds present in solution A. [2] (d) Explain why the sulfate ion cannot be present in solution A. [1] Total [6] excess aqueous sodium hydroxide warm gently aqueous ammonia aqueous sodium hydroxide colourless solution A white precipitate B white precipitate C aqueous silver nitrate no precipitate white precipitate insoluble in excess aqueous sodium hydroxide white precipitate is insoluble in dilute nitric acid dilute nitric acid colourless and pungent gas D evolved which turned moist red litmus blue add aluminium powder to the mixture and warm gently no visible change

2015 End-of-Year Examination Secondary Three 7 Nanyang Girls’ High School Setters: CHG, NHK Chemistry [Turn Over] A6 A series of experiments were carried out to compare the rate of reaction of acid with zinc under different conditions. In each experiment, 13.5 g of zinc and 25 cm3 of acid were used. The conditions for each experiment are shown in the table below. experiment form of zinc acid used concentration of acid used / mol dm−3 A large pieces HCl 0.200 B powder HCl 0.200 C powder HCl 0.100 D powder CH3COOH 0.100 E large pieces H2CO3 0.100 The gas given off was collected and its total volume was measu red every 15 seconds for 10 minutes. The results obtained were plotted as shown. (a) State the two factors that affected the rate of reaction in the five experiments above. [2] (b) For each of the experiments A to E, state which of the curves I to V, corresponds to the results obtained. experiment A B C D E curve [4] Total [6] time / min volume of gas / cm3

2015 End-of-Year Examination Secondary Three 8 Nanyang Girls’ High School Setters: CHG, NHK Chemistry [Turn Over] Section B Answer three questions from this section on the writing papers provided. The last question is in the form of either/or and only one of the alternatives should be attempted. Each question carries ten marks. B7 (a) Magnesium silicide is prepared by heating a mixture of magnesium and silicon. Write a chemical equation for the formation of magnesium silicide. [1] (b) When magnesium silicide is reacted with dilute hydrochloric acid, a very reactive compound of silane, with a c