美国化学高考题

1、READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fl uid. DO NOT WRITE IN ANY BARCODES. Answer all questions. You may lose marks if you do not show your working or if you do not use appropriate units. A Data Booklet is provided. At the end of the examination, fasten all

2、your work securely together. The number of marks is given in brackets at the end of each question or part question. CHEMISTRY 9701/21 Paper 2 Structured Questions AS Core May/June 2012 1 hour 15 minutes Candidates answer on the Question Paper. Additional Materials: Data Booklet UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certifi cate of Education Advanced Subsidiary Level and Advanced Level This document consists of 11 printed pages and 1 blank page. Turn over IB12 06_9701_21/3RP

3、UCLES 2012 *1182281800* For Examiners Use 1 2 3 4 5 Total 2 9701/21/M/J/12 UCLES 2012 For Examiners Use Answer all the questions in the spaces provided. 1 Oxides are compounds which usually contain oxygen combined with one other element. Oxides are classifi ed as follows. acidic alkaline amphoteric basic (a) Using these terms only, complete the table to describe the oxides of the elements of the third period of the Periodic Table sodium to sulfur. Na2OMgOAl 2O3SiO2P4O10SO2Cl 2O7 acidic 4 (b) Giv

4、e the names of two elements from sodium to chlorine which form more than one oxide. . and . 1 (c) Sodium reacts with water. (i) Describe, as fully as you can, what you would see when a piece of sodium is reacted with water. (ii) Write an equation for the reaction of sodium with water. 4 3 9701/21/M/J/12 UCLES 2012 Turn over For Examiners Use (d) Sulfur dioxide is present in small, but signifi cant, amounts in the Earths atmosphere. (i) State one way by which sulfur dioxide enters the atmosphere.

5、 (ii) Give the formula of another sulfur compound which is formed in the atmosphere from sulfur dioxide. . (iii) What are the environmental consequences of the compound you have identifi ed in (ii)? 3 (e) Sulfur dioxide is used as a food preservative. What property of sulfur dioxide enables it to act in this way? . 1 (f) Another sulfur compound which is present in the Earths atmosphere is carbonyl sulfi de, OCS. The sequence of atoms in the molecule is oxygen-carbon-sulfur and the molecule is no

6、t cyclic. (i) Draw a dot-and-cross diagram of the OCS molecule. Show outer electrons only. (ii) Suggest a value for the O C S bond angle. . 2 Total: 15 4 9701/21/M/J/12 UCLES 2012 For Examiners Use 2 Ammonium sulfate, (NH4)2SO4, is widely used as a fertiliser. In order to determine its percentage purity, a sample of ammonium sulfate fertiliser was analysed by reacting a known amount with an excess of NaOH(aq) and then titrating the unreacted NaOH with dilute HCl. (a) Ammonium sulfate reacts with

7、 NaOH in a 1 : 2 ratio. Complete and balance the equation for this reaction. (NH4)2SO4 + 2NaOH .NH3 + + 2 (b) A 5.00 g sample of a fertiliser containing (NH4)2SO4 was warmed with 50.0 cm3 (an excess) of 2.00 mol dm3 NaOH. When all of the ammonia had been driven off, the solution was cooled. The remaining NaOH was then titrated with 1.00 mol dm3 HCl and 31.2 cm3 were required for neutralisation. (i) Write a balanced equation for the reaction between NaOH and HCl. (ii) Calculate the amount, in mol

8、es, of HCl in 31.2 cm3 of 1.00 mol dm3 HCl. (iii) Calculate the amount, in moles, of NaOH in 50.0 cm3 of 2.00 mol dm3 NaOH. (iv) Use your answers to (i), (ii) and (iii) to calculate the amount, in moles, of NaOH used up in the reaction with (NH4)2SO4. 5 9701/21/M/J/12 UCLES 2012 Turn over For Examiners Use (v) Use your answer to (iv) and the equation in (a) to calculate the amount, in moles, of (NH4)2SO4 that reacted with NaOH. (vi) Use your answer to (v) to calculate the mass of (NH4)2SO4 that

9、reacted with NaOH. (vii) Hence, calculate the percentage purity of the ammonium sulfate fertiliser. 7 Total: 9 6 9701/21/M/J/12 UCLES 2012 For Examiners Use 3 Methanol, CH3OH, is considered to be a possible alternative to fossil fuels, particularly for use in vehicles. Methanol can be produced from fossil fuels and from agricultural waste. It can also be synthesised from carbon dioxide and hydrogen. (a) Defi ne, with the aid of an equation which includes state symbols, the standard enthalpy change of formation of carbon dioxide. equation defi nition . . . 3 (b) Relevant values for the reaction that synthesises methanol are given in the table. compound CO2(g)394 CH3OH(g)201 H2O(g)242 (i) Use these values to calculate for this synthesis of methanol. Include a sign in your answer. CO2(g) + 3H2(g) CH3OH(g) + H2O(g) = .kJ mol1 (ii) Suggest one possible environmental advantage of this reaction. Explain your answer. 5

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