Reinvestigation of the Henry’s law constant for hydrogen peroxide withtemperature and acidity variation
Daoming Huang , Zhongming Chen
DOI:
Received May 11, 2009,Revised June 12, 2009, Accepted , Available online
Volume 22,2010,Pages 570-574
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Hydrogen peroxide is not only an important oxidant in itself; it also serves as both sink and temporary reservoir for other important
oxidants including HOx (OH and HO2) radicals and O3 in the atmosphere. Its partitioning between gas and aqueous phases in the
atmosphere, usually described by its Henry’s law constant (KH), significantly influences its role in atmospheric processes. Large
discrepancies between the KH values reported in previous work, however, have created uncertainty for atmospheric modelers. Based
on our newly developed online instrumentation, we have re-determined the temperature and acidity dependence of KH for hydrogen
peroxide at an air pressure of (0.960 0.013) atm (1 atm = 1.01325 105 Pa). The results indicated that the temperature dependence
of KH for hydrogen peroxide fits to the Van’t Ho equation form, expressed as lnKH = a/T – b, and a = – H/R, where KH is in M/atm
(M is mol/L), T is in degrees Kelvin, R is the ideal gas constant, and H is the standard heat of solution. For acidity dependence,
results demonstrated that the KH value of hydrogen peroxide appeared to have no obvious dependence on decreasing pH level (from
pH 7 to pH 1). Combining the dependence of both temperature and acidity, the obtained a and b were 7024 138 and 11.97 0.48,
respectively, H was (58.40 1.15) kJ/(K mol), and the uncertainties represent . Our determined KH values for hydrogen peroxide
will therefore be of great use in atmospheric models.
