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The Stokes-Einstein relation in water/methanol solutions
C Corsaro1, E Fazio1, D Mallamace1
1Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Università di Messina, Viale F. Stagno d' Alcontres, 31, 98166 Messina, Italy.
The Journal of Chemical Physics
|June 24, 2019
Summary
Water and methanol solutions exhibit nonideal behavior due to hydrogen bonding and hydrophobic interactions. The study examines transport properties, revealing violations of the Stokes-Einstein relation that vary with solution concentration.
Area of Science:
- Physical Chemistry
- Thermodynamics
- Fluid Dynamics
Background:
- Water and methanol solutions form nonideal mixtures due to hydrogen bonding and hydrophobic interactions.
- Solution nonideality affects dynamic and thermodynamic properties, influenced by temperature and concentration.
Purpose of the Study:
- Investigate the thermal behavior of water-methanol mixtures using transport quantities.
- Analyze self-diffusion and viscosity data across various methanol concentrations and temperatures.
- Interpret results using mode coupling theory to understand deviations from ideal behavior.
Main Methods:
- Employed the Stokes-Einstein relation to analyze transport properties.
- Measured self-diffusion coefficients and viscosity.
- Studied solutions with methanol molar fractions of 0.22, 0.5, and 0.7 at varying temperatures.
Main Results:
- Observed nonideal behavior in water-methanol solutions.
- Demonstrated that the Stokes-Einstein relation is violated.
- Showed that the extent and manner of Stokes-Einstein relation violation depend on methanol concentration.
Conclusions:
- The nonideality of water-methanol solutions significantly impacts their transport properties.
- Mode coupling theory provides a framework for understanding the observed deviations from the Stokes-Einstein relation.
- Concentration-dependent violations of the Stokes-Einstein relation highlight the complex dynamics of these mixtures.
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