Water Structure, Quantum Nature of Hydrogen Bonds and Diffusion of Water Molecules in Chloride Aqueous Solutions

Abstract

A large variety of water properties is caused by the peculiarities of water clusters and water hydrogen bonds which are quantum mechanical in nature due to a small mass of hydrogen atoms. The concentration dependences of the diffusion coefficient D for aqueous solutions were found using the DOSY 2D NMR method. It was shown that with exception of barium chloride solution, which exhibits an anomalous concentration behavior of D in the concentration range 0–10 mg/ml, for two other solutions D decreases with increasing of the concentration. On basis of the generalized Stokes–Einstein equation the following correlation lengths for water and chloride solutions of the concentration $c = 100$ mg/ml were obtained: $\left\langle \xi \right\rangle_{{H_{2} O}} {\kern 1pt} = {\kern 1pt} 1.0 7$ Å, $\left\langle \xi \right\rangle_{{MgCl_{2} }} {\kern 1pt} = {\kern 1pt} 0. 9 3$ Å, $\left\langle \xi \right\rangle_{{CaCl_{2} }} {\kern 1pt} = {\kern 1pt} 1.04$ Å and $\left\langle \xi \right\rangle_{{BaCl_{2} }} {\kern 1pt} = {\kern 1pt} 0. 8 4$ Å. In the model of equivalent clusters of radius R the formula for estimation of the averaged time interval $\tau_{0}$ between decay and creation of the clusters $\tau_{0} \; = \;\tau_{1} \left[ {\left( {R - \xi_{0} } \right)/\left( {\left\langle \xi \right\rangle - \xi_{0} } \right) - 1} \right]$ was proposed ($\tau_{1}$ is the cluster lifetime and $\xi_{0}$ is the correlation length of the water without clusters). It was shown that for pure water $\tau_{0} \approx 10^{ - 8} - 10^{ - 7} {\text{s}}$.