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The saponification of ethyl acetate was measured by conductimetry at different temperatures within a batch reactor. A new mathematical model for obtaining concentration profiles from conductivity was presented and used for reaction-kinetics' determination. The Arrhenius parameters (A, E a ) showed good agreement with the previously published values. Basic transition-state theory was used for obtaining the Gibbs energy ( G ‡ ), the enthalpy ( H ‡ ), and the entropy ( S ‡ ) of activation. The low enthalpy of activation and negative entropy of activation were consistent with a reaction pathway when forming a transition-state complex. The suggested mechanism involves OH − , acting as a general base for removing proton from one of the hydroxide hydrating water, placed directly between it and the ester. The nucleophile from the water then attacks at the electrophilic C of the ester, breaking the π bond, and creating a tetrahedral intermediate. C

The micellization process of model cationic surfactants, alkyltrimethylammonium bromides with different alkyl chain length: dodecyl-(C12TAB), tetradecyl-(C14TAB) and hexadecyl- (C16TAB) has been investigated by the conductivity measurements over the temperature range 298.2 K–313.2 K. Understanding micelle formation requires its complete thermodynamic parameters, which were estimated by applying the proposed alternative derivation of pseudo-phase model. The critical micelle concentration (CMC), standard free Gibbs energy (ΔmicG0), enthalpy (ΔmicH0) and entropy (ΔmicS0) of micellization were analysed as a function of the increase in alkyl chain and temperature. At lower temperatures, the micellization in each case was found to be entropy-driven due to the increase in bulk water entropy. London or dispersion interactions are responsible for the cohesion between the apolar chains in the micelles and increase as the length of chains increases. ΔmicH0 reflects the contribution of London interactions, electrostatic repulsion between head groups and removing the alkyl chains from water (dehydration of CH2 and CH3 groups). As the temperature is increased, less energy is required for dehydration and hence the enthalpy of micellization became more exothermic and its effect more significant. The enthalpy-entropy compensation phenomenon was observed for all studied surfactants.

The corrosion resistance of AISI 420 stainless steel in 0.1 mol L −1 H 2 SO 4 + 0.1 mol L −1 Na 2 SO 4 solutions at different pH-values and the inhibiting effect of Ce 3+ ions was studied using electrochemical polarization methods. The results reveal decreasing of the corrosion rate with an increasing the pH of the solution, which demonstrates the progressive protective character of the inhibitor used. At pH lower than 3.33, the corrosion inhibition was most probably a result of the competitive adsorption of Ce 3+ with H + ions on the cathodic sites of the electrode surface, and it was found to be dependent on the relative concentration of H + /Ce 3+ . The peroxide generated from the oxygen reduction reaction at pH 3.33 was found to be capable oxidize trivalent cerium (Ce) to the tetravalent state. As obtained hydroxide precipitates act as diffusion barrier hindering the corrosion processes, whereafter a spontaneous passivity occurs on the steel surface at this pH.