Hydration numbers of perchloric acid: Estimation method based on the Raoult law

Infrared Spectra in the 1000–100 cm−1 Region Combined with 4000–3000 cm−1 Region to Evaluate the States of Water

“…Theoretically, Raoult's law is used to evaluate the state of water molecules in ideal and/or dilute solutions. 31 When this law is valid, the mole fraction of water and a w values exhibit a linear relationship. However, in an actual aqueous solution, with increasing ion concentration, the ions interact with the water molecules, binding them and accelerating their movement.…”

Vibrational and impedance analysis of the β-stannic acid samples plasticized by perchloric acid

“…Model [ 35 ] does not impose any restrictions on the number of water molecules between which the proton is distributed in a dilute aqueous solution, although physicochemical data indicate that such restrictions actually exist. The hydration numbers of the proton h in perchloric acid were estimated using ATR IR spectroscopy method [ 41 ] and from the values of the thermodynamic activity of water [ 42 ]. Calculated on the basis of thermodynamic data the h values were plotted versus the molar ratio n = H 2 O/HClO 4 .…”

Dissociation Must Be Taken into Account in Raoult’s Law

“…Raoult’s law states that at a temperature T , the solvent vapor pressure, P , of an ideal solution is the product of the mole fraction of solvent, x solvent , and the vapor pressure of pure solvent at the same temperature, P °: P = x solvent P ° There are many scientific papers focusing on how Raoult’s law should be explained or applied to aqueous salt solutions. − Some authors have stated that it should not be included in the introductory chemistry curriculum. , This has been the subject of controversy, ,,,− and papers have been published focusing on the application of thermodynamic principles − or on how to calculate the mole fraction of the solvent. ,− , In this context, there is no doubt that the effect of solute dissociation, which can be accounted for by the van’t Hoff factor, i , defined as the ratio of moles of particles formed by the solute in solution to moles of dissolved solute, must be considered. Even the need to take into account the concept of “free water”, i.e., the total amount of water (in moles) minus any amount bound to solutes, and the actual number of particles formed per mole of solute to evaluate the solvent concentration has been pointed out. − ,− , However, the fact that most general chemistry textbooks explicitly include the effect of dissociation in the calculation of the other colligative properties but not for vapor pressure depression may lead to a misunderstanding at the introductory levels of chemistry, with the consequence that the same expression for vapor pressure is used for aqueous salt solutions as for ideal solutions, without considering dissociation.…”