11177 16 Ammonium perchlorate, NH4ClO4, is used in solid rocket fuels. It can be formed by reacting ammonia with the strong acid perchloric acid as follows: NH3  +  HClO4  "  NH4ClO4 (a) (i) What is the oxidation number of chlorine in ammonium perchlorate? [1] (ii) Explain whether a solution of ammonium perchlorate is acidic, alkaline or neutral. [2] (b) Ammonium perchlorate decomposes, when heated, to produce a mixture of hydrogen chloride, nitrogen, oxygen and water. (i) Write the equation for the thermal decomposition of ammonium perchlorate. [2] (ii) Calculate, to two significant figures, the volume of gas produced by the complete decomposition of 11.75 g of ammonium perchlorate at 250 °C and one atmosphere pressure. (1 mole of a gas occupies 42 dm3 at 250 °C and one atmosphere pressure) [3] 11177 [Turn over (c) Ammonia solution can be used to make buffers by adding ammonium chloride. (i) Explain what is meant by the term buffer solution. [2] (ii) Explain, including equations, how a mixture of ammonia and ammonium chloride solutions acts as a buffer. [4] 11177 (d) Ammonia is produced by the Haber process as follows: N2(g)  +  3H2(g)  ?  2NH3(g) The table below gives the ∆fH and S values for the reactants and products. ∆fH /kJ mol−1 S /J mol−1 K−1 N2 0 192 H2 0 131 NH3 −46.2 193 (i) Calculate, to three significant figures, ∆S for the reaction. [1] (ii) Calculate, to three significant figures, ∆G for the reaction at 298 K. [2] (iii) At what temperature does the reaction become feasible? Give your answer to three significant figures. [2] (iv) State one factor which may prevent the reaction from occurring at the temperature calculated in part (iii). [1] THIS IS THE END OF THE QUESTION PAPER 11177 BLANK PAGE DO NOT WRITE ON THIS PAGE 11177 11177 BLANK PAGE DO NOT WRITE ON THIS PAGE 230406 Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright holders may have been unsuccessful and CCEA will be happy to rectify any omissions of acknowledgement in future if notified. DO NOT WRITE ON THIS PAGE © CCEA 2017 SYMBOLS OF SELECTED IONS SOLUBILITY IN COLD WATER OF COMMON SALTS, HYDROXIDES AND OXIDES Negative ions Soluble All sodium, potassium and ammonium salts All nitrates Most chlorides, bromides and iodides EXCEPT silver and lead chlorides, bromides and iodides Most sulfates EXCEPT lead and barium sulfates Calcium sulfate is slightly soluble Insoluble Most carbonates EXCEPT sodium, potassium and ammonium carbonates Most hydroxides EXCEPT sodium, potassium and ammonium hydroxides Most oxides EXCEPT sodium, potassium and calcium oxides which react with water Name Symbol Ammonium Chromium(III) Cr3+ Copper(II) Cu2+ Iron(II) Fe2+ Iron(III) Fe3+ Lead(II) Pb2+ Silver Ag+ Zinc Zn2+ Name Symbol Butanoate C3H7COO- Carbonate Dichromate Ethanoate CH3COO- Hydrogencarbonate Hydroxide OH– Methanoate HCOO– Nitrate NO Propanoate C2H5COO– Sulfate Sulfi te New Specifi cation Positive ions © CCEA 2017 For fi rst teaching from September 2017 Data Leafl et Including the Periodic Table of the Elements For the use of candidates taking Science: Chemistry, Science: Double Award or Science: Single Award Copies must be free from notes or additions of any kind. No other type of data booklet or information sheet is authorised for use in the examinations gcse examinations chemistry 227 89 139 57 256 101 223 87 226 88 261 104 262 105 266 106 264 107 277 108 268 109 271 110 272 111 140 58 141 59 144 60 145 61 150 62 152 63 157 64 159 65 162 66 165 67 167 68 169 69 173 70 175 71 232 90 231 91 238 92 237 93 242 94 243 95 247 96 245 97 251 98 254 99 253 100 254 102 257 103 133 55 137 56 178 72 181 73 184 74 186 75 190 76 192 77 195 78 197 79 201 80 89 39 91 40 103 45 85 37 88 38 93 41 96 42 98 43 101 44 106 46 108 47 112 48 131 54 222 86 210 85 210 84 209 83 207 82 204 81 84 36 79 34 73 32 40 20 39 19 45 21 48 22 51 23 52 24 55 25 56 26 59 27 59 28 64 29 65 30 11 5 12 6 14 7 16 8 19 9 20 10 4 2 40 18 35.5 17 32 16 31 15 28 14 27 13 70 31 75 33 80 35 115 49 119 50 122 51 128 52 127 53 23 11 24 12 7 3 9 4 * 58 – 71 Lanthanum series † 90 – 103 Actinium series a = relative atomic mass x = atomic symbol b = atomic number THE PERIODIC TABLE OF ELEMENTS Group a bx * † 1 1 1 2 3 4 5 6 7 0 285 112 Copernicium (approx)