Raman spectroscopic study of aqueous (NH4)2SO4 and ZnSO4 solutions

The Raman spectra of the v1-SO42− band in 0.5–2.5 molar aqueous (NH4)2SO4 and ZnSO4 solutions in the temperature range 25–85°C were studied. The molar scattering coefficient of the v1 band is the same for all forms of sulfate in (NH4)2SO4 and ZnSO4 solutions and is independent of temperature up to 85°C. The v1 band profile is symmetrical in (NH4)2SO4 solutions. In ZnSO4 solutions, a shoulder appears on the high frequency side which increases slightly in intensity with increasing concentration and temperature. This high frequency component is attributed to the formation of the contact ion pair (Zn2+·SO42−). The enthalpy of formation for the contact ion pair is estimated from the Raman data to be approximately 3 kJ-mol−1 which is in reasonable agreement with measurements by other methods.

[1]  R. Hester,et al.  A Raman Spectrophotometric Comparison of Interionic Association in Aqueous Solutions of Metal Nitrates, Sulfates, and Perchlorates , 1964 .

[2]  Felix Franks,et al.  Water:A Comprehensive Treatise , 1972 .

[3]  R. Hester,et al.  Raman Spectra of Aqueous Solutions of Indium Sulfate, Nitrate, and Perchlorate , 1963 .

[4]  R. Aruga.  Thermodynamics of association of selenate and sulfate with bivalent metals. Calculation, by calorimetric data, of the water molecules displaced from a cationic sphere , 1978 .

[5]  J. Waugh,et al.  Advances In Magnetic Resonance , 1974 .

[6]  D. Irish,et al.  Equilibriums and proton transfer in the bisulfate-sulfate system , 1970 .

[7]  F. Millero,et al.  The volume and compressibility change for the formation of transition metal sulfate ion pairs at 25°C , 1980 .

[8]  D. Irish,et al.  Vibrational Spectral Studies of Solutions at Elevated Temperatures and Pressures. IV. Raman Spectra of Aqueous Zinc Nitrate Solutions , 1983 .

[9]  A. Ben-Naim.  Water and Aqueous Solutions: Introduction to a Molecular Theory , 1974 .

[10]  W. A. Adams,et al.  High-pressure laser raman spectroscopic investigation of aqueous magnesium sulfate solutions , 1974 .

[11]  Barry G. Oliver,et al.  Raman spectroscopic evidence for contact ion pairing in aqueous magnesium sulfate solutions , 1973 .

[12]  Chris W. Brown,et al.  Sodium and magnesium sulfate ion pairing. Evidence from Raman spectroscopy , 1972 .

[13]  K. Breitschwerdt,et al.  Ultrasonic Relaxation Studies in Aqueous Solutions of 2–2 Electrolytes , 1970 .

[14]  A. I. Popov,et al.  Zinc-67 NMR study of zinc ions in water and in some nonaqueous and mixed solvents , 1982 .