Enthalpies of formation of Cr³⁺(aq) and the inner sphere complexes CrF²⁺(aq), CrCl²⁺(aq), CrBr²⁺(aq), and CrSO₄⁺(aq)

Abstract

INGEMAR DELLIEN and LOREN G. HEPLER. Can. J. Chem. 54, 1383Chem. 54, (1976. We have carried out calorimetric measurements leading to AHfO = -60 kcal mol-1 for Cr3+(aq). Further calorimetric measurements have led to enthalpies of reaction of Cr3+(aq) with HF(aq), C1-(aq), Br-(aq), and SO4'-(aq) to form the 'inner sphere' complexes CrF2+(aq), CrCI2+(aq), CrBr2+(aq), and CrS04+(aq). values ranging from -5 1 to -62 kcal mol-I for Cr3+(aq). We (2) selected AH; = -57 kcal mol-' for Cr3+(aq) and the corresponding

Thermodynamic properties and environmental chemistry of chromium

“…Based on data presented byThusius (1971),Hale and King (1967), and D e l l i e n andHepler (1976), I e s t i m a t e t h a t A G O = 1.14 k c a l m o l -l , AH 0 = 6.29 k c a l mol-' and AS" = 17.28 c a l K -l mol-' f o r t h e r e a c t i o n , 3 + C r (aq) + c l -( a q ) = crc12+(aq,is)(12) These data l e a d t o AG; 2981 = -84.13 k c a l mol-l, = -94.44 k c a l "01-' + and S; g8 = -33.47 c a l K-mol-' f o r CrC12 (aq,is). The o u t e r sphere complex forms i n t h e r e a c t i o n , ~r(H,o),~+(aq) + ~1 -(aq) = C~( H~O )~C I '+(aq .os) (13) ( l o g K = -0.05, v = 1.0 ( D e l l i e n e t al., 1976a)).T h i s leads t o A G ;~~~ = --425 k c a l m0l-' f o r C~( H~O )~C I '+(aq ,OS) .…”

Why halides enhance heterogeneous metal ion charge transfer reactions

“…Cr 3+ complexes with anions in its rst solvation sphere, and charge transfer is predicted to take place through a Cr 3+ -anion bridge on Hg. 15,35 We predict that Cr 3+ behaves similarly to V 3+ on Hg(111), where halides increase the DG ‡ des relative to sulfate in the same order (*OH < *Cl < *Br < *I), Fig. 3b.…”

Improvements in Estimated Entropies and Related Thermodynamic Data for Aqueous Metal Ions

“…Another value can be obtained from the enthalpy of oxidation of Cr 2+ (aq) by Fe 3+ (aq) in 0.5 M HClO 4 , and this gives Δ H ○̵ (5) = −111.1 kJ mol –1 . The discrepancy between the two values of Δ H ○̵ (5) can be expressed in terms of entropies.…”