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

Abstract

Kinetic studies on the reaction of vanadium(III) with mercury(II), 2V^III+ 2Hg^II→ 2V^IV+(Hg^I)₂, in perchloric acid solutions of ionic strengths 2·0M(LiClO₄) and 3·0M(NaClO₄) are consistent with the mechanism (i)–(iii). V^III+ Hg^II [graphic omitted] V^IV+ Hg^I(i), V^III+ Hg^I [graphic omitted] V^IV+ Hg⁰(ii), V^IV+ Hg^I [graphic omitted] V^V+ Hg⁰(iii), Subsequent reactions Hg⁰+ Hg^II→(Hg^I)₂, and V^III+ V^V→ 2V^IV 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 V^III+ Hg^II→ V^V+ Hg⁰ as an alternative to (iii), the consecutive one-electron changes V³⁺→ VO²⁺→ VO₂⁺ are considered more likely.