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CHEMICAL PROJECTS Research Ideas for Young Chemists JAY A. YOUNG, King's College, Wilkes-Barre, Penno. JOHN K. TAYLOR, National Bureau of Standards, Worhington, D. C.
Demonstration
See ROWEN,D. M.,J. C h m . Educ., 26, 330 (1949). Isomers with the same empirical composition often exhibit substantial differences in their chemical properties. Similarly, widely sepzrated members of a homologous series show marked differences. A series of three experiments with normal and with tertiary-hutyl bromide is described, illustrating this fact. These involve the replacement of the Br, in each isomer, with I, with NOI, and with OH. The reactivities of the two isomers are not compsrahle in all three experiments. Questionr: Find two other isomeric compounds which show differences
in their reactivities with various reagents which you select. Experiment 28 in the 2nd edition of the CHEM Study laboratory manual illustrates another type of isomeric etfect on reactivity. I s i t true that in 8, homologous series, the properties of the members of the series show a gradual variation, as the molerulnr weight increases with earh CH. unit? Account for differences you ohserve in the properties of two isomers, or in the members of 8, homologous s e r i ~ s . Devise laboratory tests to verify your explanation.
The Direct Reactions of Solids See FEIOL,F., ET AL., J. Chem. Educ., 2 1 , 18-24, 32 (1944) I n this article, fourteen different reactions all of which take place in the absence of a solvent are described. Some of the reactions are nniqne, and others represent types of reactions with different possible variations (many of which are suggested by the authors). Typical examples of the fourteen different reactions are, the reaction between magnesium oxide and any one of several metal sulfates, the formation of complex compounds, the reaction between basic and acidic oxides, the decomposition of copper(1) iodide by a catalyst, and the reaction between mercury(I1) iodide and eopper(1) iodide or silver iodide. Few nmers . which have been discussed in this series will suggest as many different ideas for investigations to interested, competent students as tthis paper. It is truly full of provocative
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suggestions far students who wish to study chemistry and who seek challenging suggestions for their own laborstory investigations. Most of the suggested experiments arc easily performed, requiring only a burner and a crucible. However, to answer the question suggested helon, other equipment of the sort commonly found in most elementary laboratories will he needed. For thorough investigations, of course, sophisticated instruments will he helpful, though probably not essential. Question: Select any reaction explicitly mentioned, or indirectly 8uggested, in the article. Carr,v out the reaction and determine by quantitative measurements the balanced equation which describes the reaction you have chosen for study.
Demonstration of Some Properties of Prussian Blue See KOHN,A%., J . Chem. Educ., 2 0 , 198 (1943). Pmssian blue, Fe41Fe(CN).13, can he reduced to iron(I1) hexacyanoferrate(II), FedFe(CN)d by hyposulfurous acid, H2S200. An acidified solution of sodium hyposulfite furnishes the necessary hyposulfurous acid. The reaction is rapid and complete, and the change from 8. blue insoluble substance to a white insoluble substance is striking. Further, Prussian blue will react metathetically with many substances which contain ligand donors, such as potassium oxalate. I n this case, two soluble compounds, tetrapotassium hexacyanoferrate and tripotassium trioxalatoferrate are formed. Questions: Can you determine the reactions which occur when Pruasisn blue is reduced by hyposulfurous acid? What other reducing agents will reduce Prussian blue to
iron(I1) hexscyanoforrate(II)? Determine the reactions which take place when a differentreducing agent is used. How many oxidizing agents can you find which will oxidize iron(I1) hexacyanoferrate(I1) to Prussian blue? Can you suggest a plausible reaction scheme to account for one of these oxidations? Show that such a. scheme is or is not pls,usihle, by furtherlaboratory work. As noted in the article, the iron(II1) ion of Prussian blue will accept ligands, such as the oxalate ion, in place of the hexacyanoferrate(I1) ligand, with which it is associated in Pmssian blue. What other ligands, in addition to the oxslate ion, can you find which will displace the hexaeyanoferrate(I1) ion from Prussian blue? (Continmd on page AI39)
Volume 40, Number 2, February 1963
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