Teachers' guide 2 - National STEM Centre

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280 Appendix 2 The components required are: From Radiospares, 4-8 Maple Street, London WI 7 4 mm sockets I kQ!W carbon resistor I SPST biased switch (A)} t t' I I SPST switch (B) no essen la and 4 oz (100 m) Constantan wire (S.W.G. 28) I metre rule or metre scale paper also I polythene box Wood for mounting potentiometer wire I jockey made from small screwdriver and 50-0-50 flA galvanometer (Shinohara Inin square from G. W. Smith, 3 Lisle Street, London WC2, is a suitable cheap meter (about £1.50) A 2 V accumulator and standard cell are also required c A potentiometer using a helical potentiometer instead of a straight wire can be used. Details are given in the Nuffield Advanced Chemistry Apparatus and materials list obtainable from. the Association for Science Education, College Lane, Hatfield, Herts. 11 Hydrogen electrode (Topic 15) A number of quite simple versions of this electrode can easily be constructed. Three possible designs are shown in figure A.20. Expense is saved if copper wire is soldered to a short length of platinum wire (use zinc chloride/hydrochloric acid flux and ordinary soft solder). The platinum wire must be covered with electrolytically-deposited platinum over the lower inch or so. This is done by using another platinum wire as a second electrode, and immersing both in a 3 per cent solution of platinum(Iv) chloride containing a small proportion (approximately 0.05 per cent) of lead acetate, connecting the electrodes to a d.c. supply (about 4 V), and reversing the current every half minute for 15 minutes. The electrodes are then washed with distilled water, and occluded chlorine is removed by placing the electrodes in sodium acetate solution (approximately M) and again passing current for 15 minutes, reversing every half minute. The electrodes are then washed with distilled water and stored in distilled water when not in use.
Apparatus, materials, and reagents Figure A.20 Types of hydrogen electrode. L---Cuwire sealing wax soldered joint Ptwire Ptwire hole in glass tubing mercury A cylinder is most convenient supply of hydrogen gas but must be fitted with a reducing valve, in order to provide a very slow stream of gas. Alternatively, a filter flask can be used as an aspirator (see figure A.21). This can be filled from a cylinder or from a suitable gas generating apparatus (in this case put dilute permanganate solution and a little dilute acid in the aspirator flask to remove impurities liable to poison the platinum electrode). wire 281
Page 1 and 2: Appendix 1 Nomenclature, units, and
Page 3: Nomenclature, units, and abbreviati
Page 6 and 7: 262 Appendix 2 Rubber caps for 100
Page 8 and 9: 264 Appendix 2 Adjustment will be r
Page 10 and 11: 266 Appendix 2 Construction The ins
Page 12 and 13: 268 Appendix 2 FigurcA.7 Box and li
Page 14 and 15: 270 Appendix 2 The box is then furt
Page 16 and 17: 272 Appendix 2 polaroid cork protra
Page 18 and 19: 274 Appendix 2 light, so the instru
Page 20 and 21: 276 Appendix 2 Before these curves
Page 22 and 23: 278 Appendix 2 These can be conveni
Page 26 and 27: 282 Appendix 2 screw clip Figure A.
Page 28 and 29: 284 Appendix 2 solutions required f
Page 30 and 31: 286 Appendix 2
Page 32 and 33: 288 Appendix 3 For this course a nu
Page 34 and 35: 290 Appendix 3 By the use of rubber
Page 36 and 37: 292 Appendix 3 For further informat
Page 38 and 39: 294 Appendix 3 Transparencies have
Page 40 and 41: 296 Appendix J Other film loops are
Page 42 and 43: 298 Appendix 3 display board (figur
Page 45 and 46: Appendhc4 Safety A correct attitude
Page 47 and 48: Safety c Storage of chemicals i Onl
Page 49 and 50: Safety Cuts - Staunch the bleeding
Page 51 and 52: Name benzoyl chloride bromine bromo
Page 53 and 54: Name 2-naphthol nitric acid nitro b
Page 55 and 56: Appendix 5 Examinations and tests T
Page 57 and 58: Examinations and tests In many resp
Page 59 and 60: Examinations and tests available to
Page 61 and 62: Examinations and tests The form of
Page 63 and 64: Examinations and tests in order to
Page 65 and 66: Examinations and tests Information
Page 67 and 68: Examinations and tests Example A Re
Page 69: Examinations and tests Example B An
Page 72 and 73: 328 Appendix 6 most effective way o
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330 Appendix 6 Programme writers ar
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332 Appendix 6 5 Remedial programme
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334 Appendix 6 non-experimental pro
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336 Appendix 6 It is generally agre
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338 Reference sources and bibliogra
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340 References sources and bibliogr
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342 Reference sources and bibliogra
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Index References to specific salts
Page 91 and 92:
Index endothermic reactions, equili
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Index paper chromatography, 218, 21
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Acknowledgements The Nuffield Found
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Acknowledgements Chemistry teachers
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Teachers' guide 2 - National STEM Centre

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