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Title: Kinetics and mechanism of oxidation of formaldehyde by aquamanganese(III) ions
Authors: Mehta, Mahendra
Nagori, Ratan Raj
Mehrotra, Raj N.
Issue Date: Mar-1998
Publisher: NISCAIR-CSIR, India
Abstract: Kinetics of oxidation of formaldehyde to formic acid by MnmIII(aq) ions in perchlorate medium indicates an order less than one in HCHO, and the rate is independent of [H+]. The pseudo-first order rate constant kobs (S-I) ([HCHO] » [MnIII)) is retarded by addition of [Mn2+] at constant ionic strength (4 mol dm-3, NaCIO4). There is a linear correlation between kobs-I and [Mn2]. The retardation in the rate is attributed to simultaneous oxidation of HCHO by solubilised Mn(OH)4. This suggestion introduces a term second order in [MnIII] in the rate law while the reaction is first order in [MnIII]. Since the slope value of the plot between kobs-I and [Mn2+] is about ten times less than the intercept value, the slope factor having a term [MnIII]2 is negligible. This explains the observed first order dependence in [MnIII] and explains the linearity of the first order plots even up to 80% completion of the reaction. Further, the generated [Mn2+], which equals the initial [MnIII] at the end of the reaction, is unlikely to affect the equilibrium 2MnIII <=> MnIV + MnII because the initial [Mn2+] is at least 20-25 times the initial [MnIII].
Page(s): 234-238
ISSN: 0975-0975(Online); 0376-4710(Print)
Appears in Collections:IJC-A Vol.37A(03) [March 1998]

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