Thermodynamics and Reaction Rates

Pekař, Miloslav

doi:10.5772/22798

Cited by 5 publications

(3 citation statements)

References 20 publications

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“…A crucial point here is the identification of the true thermodynamic equilibrium constant with the kinetic equilibrium constant; this is the main source of certain inconsistencies, which probably cannot be fully resolved even under ideal conditions. More details are given in the review [5] and in the relevant book chapter [6]. In short, the two equilibrium constants are conceptually different.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Driving Forces and Chemical Reaction Fluxes; Reflections on the Steady State

Pekař

2020

Molecules

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Molar balances of continuous and batch reacting systems with a simple reaction are analyzed from the point of view of finding relationships between the thermodynamic driving force and the chemical reaction rate. Special attention is focused on the steady state, which has been the core subject of previous similar work. It is argued that such relationships should also contain, besides the thermodynamic driving force, a kinetic factor, and are of a specific form for a specific reacting system. More general analysis is provided by means of the non-equilibrium thermodynamics of linear fluid mixtures. Then, the driving force can be expressed either in the Gibbs energy (affinity) form or on the basis of chemical potentials. The relationships can be generally interpreted in terms of force, resistance and flux.

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Section: Introductionmentioning

confidence: 99%

Thermodynamic Driving Forces and Chemical Reaction Fluxes; Reflections on the Steady State

Pekař

2020

Molecules

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“…How fast such a change can occur is a matter of kinetics. The reaction kinetics of a change-reaction can be described as a function of both a kinetic variable and a driving force (18,19). This driving force is related to the difference in chemical potential between reactant and product, meaning that the kinetics of melting would resemble rate ,…”

Section: Theory Of Ice Meltingmentioning

confidence: 99%

Chemical Melting of Ice: Effect of Solution Freezing Point on the Melting Rate

Wå̊hlin

Klein-Paste

2016

Transportation Research Record: Journal of the Transportation R

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Icy roads in wintertime present a hazard for road users. It is therefore desirable to maintain bare roads. To achieve this, deicing chemicals are typically applied. One important property of the chemicals that are used is how fast they can melt ice. Understanding what affects the melting rate, however, is limited. An experiment was therefore designed to study how the driving force for the melting—the chemical potential difference between ice and solution—affects the chemical melting rate of ice. In this study, the driving force was represented by the solution freezing points. The experiment was performed at −5°C (23°F) by using the solutions of four chemicals: sodium chloride, magnesium chloride, and calcium chloride, as well as potassium formate. These four solutions were mixed to have four freezing points. They were −10°C (14°F), −18°C (−0.4°F), −30°C (−22°F); and the eutectic temperature of each chemical. The results showed that there was a clear correlation between solution freezing point and how fast the solution could melt ice. The solutions with the lowest freezing point melted ice four to five times faster than the solutions with the highest freezing point. The importance of solution freezing point was attributed to its direct relation to the solution chemical potential, with a low freezing point giving a large driving force for the phase change. In addition, it was found that the type of chemical plays a role on the melting rate of ice. The fastest melting chemical (potassium formate) melted ice 45% faster than the slowest melting chemical (magnesium chloride), which is attributed to potassium formate having a higher ion mobility. A higher ion mobility allows a faster transport of solute to the ice–solution interface.

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“…A crucial point here is the identification of the true thermodynamic equilibrium constant with the kinetic equilibrium constant -and this is the main source of certain inconsistencies, which probably cannot be fully resolved even under ideal conditions. More details are given in the review by Pekař (2005) and in the relevant book chapter (Pekař, 2011). In short, the two equilibrium constants are conceptually different.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Driving Forces and Chemical Reaction Fluxes; Reflections on the Steady State

Pekař¹

2020

Preprint

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Molar balances of continuous and batch reacting systems with a simple reaction are analyzed from the point of view of finding relationships between the thermodynamic driving force and the chemical reaction rate. Special attention is focused on steady state, which has been the core subject of previous similar work. It is argued that such relationships should contain, besides the thermodynamic driving force, also a kinetic factor, and are of a specific form for a specific reacting system. More general analysis is provided by means of the non-equilibrium thermodynamics of linear fluid mixtures. Then, the driving force can be expressed either in Gibbs energy (affinity) form or on the basis of chemical potentials. The relationships can be generally interpreted in terms of forceresistance-flux.

show abstract

Thermodynamics and Reaction Rates

Cited by 5 publications

References 20 publications

Thermodynamic Driving Forces and Chemical Reaction Fluxes; Reflections on the Steady State

Thermodynamic Driving Forces and Chemical Reaction Fluxes; Reflections on the Steady State

Chemical Melting of Ice: Effect of Solution Freezing Point on the Melting Rate

Thermodynamic Driving Forces and Chemical Reaction Fluxes; Reflections on the Steady State

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