TY - JOUR
T1 - Non-equilibrium thermodynamics of the gas-liquid interface
T2 - Measurement of the Onsager heat of transport for carbon dioxide at the surface of water
AU - Leonard, Daniel I.
AU - Packwood, Daniel M.
AU - Phillips, Leon F.
N1 - Funding Information:
This work was supported by the Marsden Fund, administered by the Royal Society of New Zealand, and by the United States National Science Foundation, EMSI grant CHE0431512. DMP is grateful for the award of a Top Achiever’s Doctoral Scholarship.
PY - 2011/9
Y1 - 2011/9
N2 - The Onsager heat of transport Q* for carbon dioxide at the surface of water has been determined by measuring the total gas pressure as a function of the temperature difference across a 6-mm vapour gap above the water surface, and subtracting previously measured water-vapour pressures. The metal surface above the vapour gap was conditioned with carbon dioxide prior to the measurements, to enable efficient thermal accommodation for CO2 molecules striking that surface, so that plots of ΔP against ΔT were linear for ΔT values up to at least 6 K. For liquid surface temperatures ranging from 0 to 5 °C, we find Q* = -6:9 ± 1.7 kJ mol-1. Within experimental error, the results were independent of pH over the range from 6.50 to 9.04, and of CO2 partial pressure between 13 and 46 Torr. The factor Q*=RT is -3, which implies that the fractional temperature gradient is at least three times as important as the fractional partial-pressure gradient in controlling the magnitude and direction of the steady-state CO2 flux through a water surface.
AB - The Onsager heat of transport Q* for carbon dioxide at the surface of water has been determined by measuring the total gas pressure as a function of the temperature difference across a 6-mm vapour gap above the water surface, and subtracting previously measured water-vapour pressures. The metal surface above the vapour gap was conditioned with carbon dioxide prior to the measurements, to enable efficient thermal accommodation for CO2 molecules striking that surface, so that plots of ΔP against ΔT were linear for ΔT values up to at least 6 K. For liquid surface temperatures ranging from 0 to 5 °C, we find Q* = -6:9 ± 1.7 kJ mol-1. Within experimental error, the results were independent of pH over the range from 6.50 to 9.04, and of CO2 partial pressure between 13 and 46 Torr. The factor Q*=RT is -3, which implies that the fractional temperature gradient is at least three times as important as the fractional partial-pressure gradient in controlling the magnitude and direction of the steady-state CO2 flux through a water surface.
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U2 - 10.1515/JNETDY.2011.017
DO - 10.1515/JNETDY.2011.017
M3 - Article
AN - SCOPUS:82955245478
VL - 36
SP - 273
EP - 284
JO - Journal of Non-Equilibrium Thermodynamics
JF - Journal of Non-Equilibrium Thermodynamics
SN - 0340-0204
IS - 3
ER -