Mechanism of the reaction of vanadium(III) with mercury(II) in aqueous perchloric acid solutions

Kinetic studies on the reaction of vanadium(III) with mercury(II), 2VIII+ 2HgII→ 2VIV+(HgI)2, in perchloric acid solutions of ionic strengths 2·0M(LiClO4) and 3·0M(NaClO4) are consistent with the mechanism (i)–(iii). VIII+ HgII [graphic omitted] VIV+ HgI(i), VIII+ HgI [graphic omitted] VIV+ Hg0(ii), VIV+ HgI [graphic omitted] VV+ Hg0(iii), Subsequent reactions Hg0+ HgII→(HgI)2, and VIII+ VV→ 2VIV are more rapid and are not rate determining. The rate law corresponding to (i)–(iii) is given by (iv). At low initial vanadium(IV) concentrations the [graphic omitted] second term in (iv) is negligible, but at high vanadium(IV) concentrations (>0·1M) the second term becomes dominant. Although the kinetics do not rule out the two-electron reaction VIII+ HgII→ VV+ Hg0 as an alternative to (iii), the consecutive one-electron changes V3+→ VO2+→ VO2+ are considered more likely.