Determination of Enthalpy of Vaporization of Pure Liquids by UV Spectrometry

Marin-Puga, Gustavo; Guzman, L Miguel; Hevia, Francisco

doi:10.1021/ed072p91

Cited by 5 publications

(4 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Static methods involve measurements on a liquid/vapor sample trapped in a thermostated chamber while dynamic measurements involve a thermometer immersed in the vapor rising from a pure liquid boiling under various known pressures . Both of these methods are used in the introductory undergraduate chemistry laboratory where they have evolved over time to avoid the use of mercury, use modern instrumentation (i.e., UV–vis, GC, and microwave), use simpler and less expensive equipment, and use pressure sensors to reduce the data analysis …”

Section: Introductionmentioning

confidence: 99%

Relating ΔH_vap of Organic Liquids to Intermolecular Forces: Simple Modifications of a Classic General Chemistry Experiment

et al. 2020

View full text Add to dashboard Cite

The concept of equilibrium vapor pressure plays a key role in the general chemistry curriculum; it is among the first and most easily demonstrated examples of equilibrium and frequently caps off the first semester of general chemistry where it illustrates the properties of liquids and intermolecular forces. We report here simple modifications of Levinson’s classic experiment that allow measurement of vapor pressures for organic samples at a variety of temperatures. Data analysis gives heats of vaporization which may be interpreted in terms of intermolecular attractive forces. Equipment needs are simple and readily available: a 10 mL graduated cylinder, a tall 1 L beaker, disposable graduated syringes, and a 10 in. needle or cannula bent into a “J” shape. The method uses 1 mL or less of organic sample per trial and works well for organic liquids that are immiscible with and are less dense than water. Student results are presented for the experiment conducted over three semesters as well as the impact on student learning as assessed by common exam results and end-of-semester student surveys.

show abstract

Section: Introductionmentioning

confidence: 99%

Relating ΔH_vap of Organic Liquids to Intermolecular Forces: Simple Modifications of a Classic General Chemistry Experiment

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Research has shown that undergraduate students often have problems understanding chemical thermodynamics and specifically the precise meaning of terms such as enthalpy. , A simple laboratory experiment, through which students use enthalpy and enthalpy change to explain a readily observable phenomenon, can be an important mechanism to enhance their qualitative understanding of relevant concepts . Usually, the teaching of enthalpy of vaporization is based on the use of measured vapor pressures in the Clausius–Clapeyron equation, , and mostly for pure organic liquids and solutions. − In this article, for the first time, a different approach was used and it presented a novel and simple laboratory experiment to determine the Δ H vap values of salt solutions by measuring simple, steady-state temperatures, which was directly related to evaporative cooling. This approach is particularly informative for undergraduate chemistry and physics students.…”

mentioning

confidence: 99%

Determining the Enthalpy of Vaporization of Salt Solutions Using the Cooling Effect of a Bubble Column Evaporator

Fan¹,

Pashley²

2016

J. Chem. Educ.

View full text Add to dashboard Cite

The enthalpy of vaporization (ΔH vap) of salt solutions is not easily measured, as a certain quantity of pure water has to be evaporated from a solution, at constant composition, and at a fixed temperature and pressure; then the corresponding heat input has to be measured. However, a simple bubble column evaporator (BCE) was used as a novel method that allowed undergraduate students to determine the ΔH vap value of a salt solution within an hour or so, because it only required temperature measurement (at a steady state) of the column solution and the inlet gas flowing into the column. In this article, by way of illustration, the ΔH vap value of a 0.5 M NaCl solution was determined using the BCE process. In this experiment the evaporative cooling effects of the column were also easily demonstrated, as the inlet air at room temperature cooled the column solution to less than 10 °C. The change that students measured directly demonstrated the endothermic process of water vaporization. The role of several basic physical chemistry concepts, such as vapor pressure, phase transition, and enthalpy, involved in this experiment can be reinforced. An unexpected property of some common salt solutions, of bubble coalescence inhibition, was also observed in this experiment.

show abstract

“…There have been 28 articles published in this Journal on vapor pressure measurements; only the ones published since 1990 are cited here (1)(2)(3)(4)(5)(6)(7)(8). Descriptions of methods for determining vapor pressure as a function of temperature are available in physical chemistry laboratory books such as Garland, Nibler, and Shoemaker (9).…”

mentioning

confidence: 99%

Enthalpy of Vaporization and Vapor Pressures: An Inexpensive Apparatus

et al. 2007

View full text Add to dashboard Cite

An inexpensive apparatus is described for the determination of the vapor pressure of a liquid as a function of temperature for the purpose of calculating enthalpy changes of vaporization. The solid-state pressure transducer is linear above 100 torr, is useful in the range -40 to 85 °C, and is calibrated using pure water. The experimental enthalpies of vaporization for ten solvents are within ca. 0 to 13% of literature values. Two different versions of the static vapor pressure apparatus are described. Also described are a simple air thermostat and an inexpensive temperature controller (±0.1 K) based on an integrated temperature sensor. The measurement time is under three hours.

show abstract

Determination of Enthalpy of Vaporization of Pure Liquids by UV Spectrometry

Abstract: Experimental procedure for determing the vapor pressure of organic liquids at several temperatures through UV absorbance; data and analysis included.

Cited by 5 publications

References 7 publications

Relating ΔH_vap of Organic Liquids to Intermolecular Forces: Simple Modifications of a Classic General Chemistry Experiment

Relating ΔH_vap of Organic Liquids to Intermolecular Forces: Simple Modifications of a Classic General Chemistry Experiment

Determining the Enthalpy of Vaporization of Salt Solutions Using the Cooling Effect of a Bubble Column Evaporator

Enthalpy of Vaporization and Vapor Pressures: An Inexpensive Apparatus

Contact Info

Product

Resources

About

Determination of Enthalpy of Vaporization of Pure Liquids by UV Spectrometry

Abstract: Experimental procedure for determing the vapor pressure of organic liquids at several temperatures through UV absorbance; data and analysis included.

Cited by 5 publications

References 7 publications

Relating ΔHvap of Organic Liquids to Intermolecular Forces: Simple Modifications of a Classic General Chemistry Experiment

Relating ΔHvap of Organic Liquids to Intermolecular Forces: Simple Modifications of a Classic General Chemistry Experiment

Determining the Enthalpy of Vaporization of Salt Solutions Using the Cooling Effect of a Bubble Column Evaporator

Enthalpy of Vaporization and Vapor Pressures: An Inexpensive Apparatus

Contact Info

Product

Resources

About

Relating ΔH_vap of Organic Liquids to Intermolecular Forces: Simple Modifications of a Classic General Chemistry Experiment

Relating ΔH_vap of Organic Liquids to Intermolecular Forces: Simple Modifications of a Classic General Chemistry Experiment