Physical Chemistry Experiment Research Articles

The Example of the Development of Multimedia Courseware Simulating Physical Chemistry Experiments

The development process of software simulating physical chemistry experiments “The determination of saturated vapor pressure of liquid” as an example was shown based on Flash 8 software as a software developing platform and Photoshop as auxiliary software. The process of elements and instruments’ formation, the connection of instruments, the production of all kinds of scenes and their animation, the recording of sound, the simulation procedures were displayed. The courseware has been used in the physical chemistry experiment teaching. The good effect is obtained from the statistics of the student evaluations.

Raman Spectroscopy as the Method of Detection for Constructing a Binary Liquid–Vapor Phase Diagram

The physical chemistry laboratory is sometimes constrained to one semester, resulting in pedagogical deficiencies for the students taking the course. The use of a multidimensional laboratory exercise offers students the opportunity to encounter multiple experimental techniques and physical chemistry concepts while not sacrificing a significant amount of time. Here, we show that the classic binary liquid–vapor phase diagram experiment can be modified to incorporate both molecular spectroscopy and quantum chemistry. Using Raman spectroscopy as a means of detection and quantum chemistry to investigate the resulting vibrational spectra, students can explore three important subject areas in one laboratory exercise.

A Simple Adsorption Experiment

The study of adsorption phenomenon is one of the most relevant and traditional physical chemistry experiments performed by chemistry undergraduate students in laboratory courses. In this article, we describe an easy, inexpensive, and straightforward way to experimentally determine adsorption isotherms using pieces of filter paper as the adsorbent and an organic dye the as the adsorbate.

An Experiment in Physical Chemistry: Polymorphism and Phase Stability in Acetaminophen (Paracetamol)

Differential scanning calorimetry analyses of two easily prepared polymorphs of acetaminophen (also known as paracetamol) are recorded. The density of the forms can be found in the literature. Rules for heats of transition, heats of fusion, and density, as well as methods for determining the solid−solid transition temperature between the forms, are used to determine whether the two forms are enantiotropic or monotropic and to determine which is the more stable form at room temperature and pressure.

Synthesis of hydrocarbons under upper mantle conditions: Evidence for the theory of abiotic deep petroleum origin

A theory of abiotic deep petroleum origin explains that hydrocarbon compounds are generated in the upper mantle and migrate through the deep faults into the Earth's crust. There they form oil and gas deposits in any kind of rock in any kind of the structural position. Until recently one of the main obstacles for further development of this theory has been the lack of reliable and reproducible experimental results confirming the possibility of the spontaneous synthesis of complex hydrocarbon systems at high pressure and temperature. Our experimental results demonstrate that abiotic synthesis of hydrocarbons under mantle conditions is a real chemical process. Different paths of hydrocarbon synthesis under mantle conditions are discussed. Obtained experimental results place the theory of the abiotic deep petroleum origin in the mainstream of modern experimental physics and physical chemistry.

Thermodynamic Exploration of Eosin−Lysozyme Binding

We developed a modular pair of experiments for use in the undergraduate physical chemistry and biochemistry laboratories. Both experiments examine the thermodynamics of the binding of a small molecule, eosin Y, to the protein lysozyme. The assay for binding is the quenching of lysozyme fluorescence by eosin through resonant energy transfer. In both experiments, students measure fluorescence quenching at constant lysozyme concentration as a function of added eosin and determine the dissociation constant, KD, and ΔG° for binding. In the physical chemistry experiment, students repeat the fluorescence measurements at several temperatures to determine the temperature dependence of ΔG°, and therefore ΔH° and ΔS° as well. Typical student results yield a KD of (28.3 ± 7.5) μmol L−1 and a binding ΔG° of (−26.04 ± 0.70) kJ mol−1 at 25 °C. ΔH° and ΔS° of binding are found to be (−4.1 ± 2.5) kJ mol−1 and (73.9 ± 8.7) J mol−1 K−1, respectively. This pair of laboratories represents an interdisciplinary module in which students in different courses examine the same system but from different perspectives and with different emphases.

SPECTRa-T: Machine-Based Data Extraction and Semantic Searching of Chemistry e-Theses

The SPECTRa-T project has developed text-mining tools to extract named chemical entities (NCEs), such as chemical names and terms, and chemical objects (COs), e.g., experimental spectral assignments and physical chemistry properties, from electronic theses (e-theses). Although NCEs were readily identified within the two major document formats studied, only the use of structured documents enabled identification of chemical objects and their association with the relevant chemical entity (e.g., systematic chemical name). A corpus of theses was analyzed and it is shown that a high degree of semantic information can be extracted from structured documents. This integrated information has been deposited in a persistent Resource Description Framework (RDF) triple-store that allows users to conduct semantic searches. The strength and weaknesses of several document formats are reviewed.

Adsorção e propriedades de volume de misturas binárias água álcool: um experimento didático com base em medidas de tensão superficial

An undergraduate physical chemistry experiment based on the drop counting method for surface tension measurements is proposed to demonstrate adsorption isotherms of binary aqueous solutions of ethanol, n-propanol, and n-butanol. Excess surface is obtained by the derivative of surface tension taken with respect to alcohol activity, after this activity calculation using van Laar equation. Laboratory class contents are surface tension, excess surface, percolation of hydrogen bonds, micelle, activity, and ideal solution.

Study of Molecular-Shape Selectivity of Zeolites by Gas Chromatography

A sorption experiment using a gas chromatograph is described that can help students understand the molecular-shape selectivity behavior of zeolites in the subnano regime. Hexane isomers are used as probe molecules to demonstrate the sorption phenomena. In the experiment, a zeolite adsorbs certain hexane isomers with molecular sizes smaller than its pore opening and rejects the isomers with greater molecular size. The sorption protocol is versatile and can be used in creative ways. Students can choose adsorbate�adsorbent pairs from 8-membered oxygen rings (8-MR), 10-MR, 12-MR zeolites and hexane isomers to build their own experimental protocol. The experiment can be used as an undergraduate analytical or physical chemistry experiment.

An Editing Activity That Prevents Mistranslation and Connection to Disease

I believe that the genetic code was the greatest discovery of the 20th century (Fig. 1). The code was worked out during the period that I was a student: a medical student at Tufts University (I dropped out after a year), a graduate student at MIT and Cornell (with Gordon Hammes), and a postdoctoral student at Stanford University (with Paul Flory). My research as a student was centered on theoretical and experimental physical chemistry, as applied to biological systems. With Hammes, I had done a spectroscopic and thermodynamic analysis of ribonuclease and its interaction with one of its ligands. I also had done both experimental and theoretical analyses of kinetic relaxation spectroscopy, inspired in part by the pioneering work of Eigen, who himself had been a mentor of Hammes. (Eigen gave lectures at Cornell that I attended, and we spent time in conversation as well. In more recent years, we have seen each other on a regular basis and continued our conversations.) With Flory at Stanford, I worked on statistical mechanics of polypeptides. All of that graduate and postdoctoral work was exciting, particularly the mathematical side that I especially loved because of its elegance, rigor, and abstraction. However, while this sort of mental activity was going on, I kept thinking about the newly discovered genetic code and aminoacyl-tRNA synthetases.

Birge–Sponer Estimation of the C–H Bond Dissociation Energy in Chloroform Using Infrared, Near-Infrared, and Visible Absorption Spectroscopy. An Experiment in Physical Chemistry

The fundamental and overtone vibrational absorption spectroscopy of the C–H unit in CHCl3 is measured for transitions from the ν = 0 energy level to ν = 1 through ν = 5 energy levels. The energies of the transitions exhibit a linearly-decreasing spacing between adjacent vibrational levels as the vibrational quantum number increases. These data are used as the basis for Birge–Sponer estimation of the dissociation energy, D0, for the C–H bond in chloroform. The value obtained from the first 5 transitions is D0 = 459 ± 8 kJ mol-1 (95% confident interval), compared to a literature value of the bond dissociation energy for this bond of 401 kJ mol-1. The error of 14.5% results from sampling only the most harmonic energy levels in the vibrational potential well.

A Safe and Efficient Technique for the Production of HCl/DCl Gas

We present a safe and efficient technique to generate HCl/DCl gas for use in the classic physical chemistry experiment that introduces students to ro-vibrational spectroscopy. The reaction involves thionyl chloride and a mixture of water and deuterium oxide to produce HCl/DCl gas with SO2 gas as a byproduct. The entire reaction is carried out in a microscale apparatus at atmospheric pressure.

Determination of Solvent Effects on Keto—Enol Equilibria of 1,3-Dicarbonyl Compounds Using NMR

The use of proton NMR to determine the equilibrium position of tautomeric 1,3-dicarbonyl compounds in various solvents has been a classic physical chemistry experiment. We are presenting an expansion of the excellent description of this experiment by Garland, Shoemaker, and Nibler. Often the assumption is made that the keto tautomer is always the more polar tautomer and hence the concentration of the keto tautomer is greater in polar solvents. However, the keto tautomers of acyclic 1,3-dicarbonyl molecules such as acetyl acetone are often not the more polar of the two tautomers, so this cannot be the only important factor that determines this equilibrium. Rather there are several factors that contribute to the tautomeric equilibrium of which solute dipole moment is just one. The study of the cyclic 1,3-diketone dimedone is especially helpful in this regard. The student is asked to analyze his/her results based on these factors. Molecular modeling is used as an aid in this analysis.

NIELS M.G. HARBOE 1918?2006

NIELS M.G. HARBOE 1918?2006

Reactivity of Ti(iv) species hosted in TS-1 towards H2O2–H2O solutions investigated by ab initio cluster and periodic approaches combined with experimental XANES and EXAFS data: a review and new highlights

This work is intended to underline how the most-advanced experimental and theoretical physical chemistry tools must be used synergistically to understand the reactivity of Ti-silicalite-1 (TS-1) in an important number of low-temperature oxidation reactions with aqueous H(2)O(2) as the oxidant. Literature results are carefully reviewed and accompanied with new, unpublished highlights of both experimental and computational origin. The first part of this work is devoted to a discussion of the defective nature of the material and to the synergic role played by Si vacancies and Ti insertion in the framework. A summary of the experimental Ti-K-edge EXAFS and XANES literature concerning the activated material in vacuo conditions is then presented and compared to the corresponding Ti geometries obtained by ab initio calculations. From such a comparison, the excellent agreement between experiment and theory is evident. A very good agreement is also obtained for the interaction with water and ammonia. For both H(2)O and NH(3), the agreement is due to the possibility to perform experiments in which the probe molecule is dosed from the gas phase, thus allowing to reach the 1 : 1 (or 1 : 2) ratio between the adsorbing Ti sites and the adsorbed molecule. Then, interaction with hydrogen peroxide is discussed, underlining the problems faced in reaching a common view between experimental and theoretical results, owing to the difficulties both in performing experiments where anhydrous H(2)O(2) is dosed on TS-1, and in taking into account the role played by the aqueous medium in the reactivity of Ti(iv) centres toward H(2)O(2) using ab initio calculations. Only once such difficulties have been overcome, by increasing the complexities of both experiments and ab initio models, is a joint-view finally obtained. Where needed, comparison with other experimental results (X-ray and neutron diffraction, NMR, IR, Raman, UV-vis and resonant Raman) is made.

Teaching Physical Chemistry Experiments with a Computer Simulation by LabVIEW

This article reports the results obtained using a computer program developed with the software LabVIEW. The program is a computer simulation of the physical chemistry experiment regarding the vapor pressure measurements of a pure liquid as a function of temperature. We also describe a system of data collecting to emphasize the similarities between the virtual and real experiment, which allows the user to read the data in the laboratory with an instrument similar to the one simulated in the virtual experience.

Principles of Solution Thermodynamics: Demonstration of Nonideal Behavior of Henry's Law. An Undergraduate Laboratory Experiment

Quantitative analysis of formaldehyde, HCHO, using the Nash reaction has seen a wide application in both the fields of environmental chemistry and medicine. Our group uses portable Nash systems both to monitor trace levels of HCHO (ppbV, 1/109) present in urban air, as well as measure HCHO in urine, an indicator of bladder cancer. Although several techniques are available for the measurement of HCHO, the rugged nature and reliability of modern, off-the-shelf wet chemical monitoring systems places them ahead of other techniques for several applications. Insightful and practical experiments in physical chemistry for the advanced undergraduate laboratory course are possible with this system. Here we discuss a technique to sample both the gas and the liquid phases of a solution of HCHO(aq), permitting the quick and direct determination of the partition coefficient for a nonideal, solute–solvent mixture. Two scenarios are presented to demonstrate factors that influence this thermodynamic ratio: (i) concentrati...

Highly accurate ignition delay apparatus for hypergolic fuel research

The efficient development of hypergolic fuels requires an interdisciplinary approach involving ab initio modeling, synthesis, and experimental physical chemistry. Candidate molecules must exhibit hypergolic ignition delay times that are fast enough to warrant further testing for safety and performance criteria. Hypergolic ignition delay apparatus has been mentioned in the open literature for six decades, but accurate, detailed, modern ignition delay hardware that uses inexpensive laboratory building blocks and a minimum of custom circuitry is still needed. This article details line-of-sight electro-optical circuitry with direct digital readout and additional oscilloscope recording that can be used to measure total ignition and chemical delay times for screening candidate fuels. We also illustrate the value of high speed video and quantum chemical calculations to supplement the ignition delay measurements for a comprehensive approach to hypergolic fuel research.

Fine-Structure Measurements of Oxygen A Band Absorbance for Estimating the Thermodynamic Average Temperature of the Earth's Atmosphere. An Experiment in Physical and Environmental Chemistry

The rotational fine structure observable in a forbidden electronic absorbance of diatomic oxygen in the earth's atmosphere can be observed as a series of minima in the solar spectrum near 762 nm wavelength. The relative intensities of these rotational fine-structure lines can be used quantitatively to estimate the average temperature of the atmosphere along the path taken by sunlight to the observer. Measured values for temperature vary from day to day and season to season and are generally far lower than ambient temperatures because of averaging over the depth of the atmosphere. These experimentally determined thermodynamic temperatures can be compared to Web-based atmospheric models for particular locations and times to illustrate the fact that they are average values.

Molecular beams with a tunable velocity

The merging of molecular beam methods with those of accelerator physics has yielded new tools to manipulate the motion of molecules. Over the last few years, decelerators, lenses, bunchers, traps, and storage rings for neutral molecules have been demonstrated. Molecular beams with a tunable velocity and with a tunable width of the velocity distribution can now be produced, and are expected to become a valuable tool in a variety of physical chemistry and chemical physics experiments. Here we present a compact molecular beam machine, capable of producing 3D spatially focused packets of state-selected accelerated or decelerated molecules.