In this laboratory, students calculated the nutritional value of common foods to assess the energy content needed to answer an everyday life application; for example, how many kilometers can an average person run with the energy provided by 100 g (3.5 oz) of beef? The optimized geometries and the formation enthalpies of the nutritional components of the food and their combustion products were calculated using molecular mechanics and a semiempirical method, AM1 or PM3, on the lab computers. These data were used to assess the energy content of common foods and compare with food label information. This general chemistry laboratory was designed for students of food engineering, yet it is applicable to students in any general chemistry course. Groups of students have successfully completed the laboratory as described here. The software was introduced, and the calculations were carried out in two, 2.5 h-long sessions.
A semiempirical model is used to analyse the results of published experiments reporting on the solid-state amorphization reactions in bilayers and multilayers formed by Gd and Co. The role of the interfacial effects in raising the free energy of the initial arrangement in a multilayered configuration, and in promoting the amorphization reaction, is studied in detail. The model explains the observation of amorphous alloys over a broad composition range in the bilayer experiments. The preferred composition obtained in the multilayer experiments is discussed critically and the model prediction of a preferred composition Gd 0.46 Co 0.54 is in good agreement with the compositions observed in recent experiments.
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