The reaction of peroxomonophosphoric acid and hydrazinium ion in acid perchlorate solutions occurs as per stoichiometry (i), and the rate law (ii) at large [NzH~'],
-d[HaPOs]/dt = [H~PO~]T[H+] (ki + kz[NzHs+]/(K& + [H']))where K& is the first acid dissociation constant of H3P05 and kl and kz are rate constants found to be 2.6 x s-' and 5.0 x lo-' M-' s-', respectively, at 35". The reaction is greatly catalyzed by iodide ions. The mechanism involves a redox cycle 1-/12 and the rate is independent of [N2H5'] in the presence of iodide ions. K& was found to be 0.55 M-' and independent of temperature.
Experimental
MaterialsSolutions of PMPA were prepared each day whenever required by the hydrolysis of peroxodiphosphate in 0.5 M HC1O4 at 45" for about 1.5 h. It was standardized iodometrically. Solutions of lithium perchlorate were prepared by neutralizing 70% HC1O4 (E. Merck) with BDH AnalaR lithium carbonate