The
POGIL-PCL project implements the principles of process-oriented, guided-inquiry
learning (POGIL) in order to improve student learning in the physical
chemistry laboratory (PCL) course. The inquiry-based physical chemistry
experiments being developed emphasize modeling of chemical phenomena.
In each experiment, students work through at least two learning cycles
in which they make predictions, collect data, model the data, and
discuss its meaning. The design of the student laboratory experiences
resembles the apprenticeship model of research because students carry
out an experiment with faculty guidance to determine which parameters
are best modified in subsequent trials of the same experiment. The
POGIL-PCL model is illustrated using the example: “What are
the kinetic parameters of a heterogeneous reaction?” Typical
student results and responses are discussed.
essentially identical results because the former method also yields an experimentally determined C2H3 entropy (55.9 (±2.6) cal mol-1 K"1) which is virtually the same as the theoretical value (55.5 (±0.5) cal mol"1 K"1). Since the enthalpy of formation and entropy determinations are coupled, high accuracy in the determination of one of these thermochemical quantities is a strong indication that the other is also accurate. In our prior study of the CH3 + HC1 reaction, a similar kinetic analysis, one which coupled our measured CH3 + HC1 rate constants with those for the Cl + CH4 reaction reported by Dobis and Benson and others,28 we also obtained exactly the correct entropy for CH3 and a heat of formation which was within ±0.2 kcal mol"1 of the most accurate prior determinations.1Recent studies using neutral reactants and products have obtained very similar values for the heat of formation of the C2H3 radical. Parmar and Benson12 obtained a C2H3 heat of formation within 1 kcal mol"1 of our value, in spite of the fact that their values for k] are lower than ours by a factor of 4. Wodtke and Lee have observed the velocity distribution of DF(u=4) from the F + C2D4 -» DF + C2D3 reaction.32 Since this information is a very sensitive function of the energetics of the reaction, it was possible to use the results of their experiments to determine a C2H3 heat of formation. They report a value of 65.6 (±0.5) kcal mol"1.
The structure of the mobile phase in liquid chromatography plays an important role in the determination of retention behavior on reversed-phase stationary materials. One of the most commonly employed mobile phases is a mixture of methanol and water. In this work, infrared and Raman spectroscopic methods were used to investigate the structure of species formed in methanol/water mixtures. Chemometric methods using multivariate curve resolution by alternating least-squares analysis were used to resolve the overlapped spectra and to determine concentration profiles as a function of composition. The results showed that the structure of these mixtures could be described by a mixture model consisting of four species, namely, methanol, water, and two complexes, methanol/water (1:1) and methanol/water (1:4). The spectral frequencies and concentration profiles found from the Raman and infrared measurements were consistent with one another and with theoretical calculations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.