Hydrogen ion acceptance by urea from hydrochloric and acetic acids: Altered dissociation constant of acetic acid

Abstract

The interaction of urea with H⁺ ion of HCl and CH₃COOH has been investigated by conductimetric and <em>p</em>H<em>-</em>metric methods. Urea significantly affects conductance and <em>p</em>H of HCl and CH₃COOH; the effective dissociation constant of the latter is appreciably altered. The urea-H⁺ binding constant has yielded the <em>pK</em>_a and <em>pK</em>_b values of 0.22 and 13.78 respectively for urea at 303K. A part of the released H⁺ ion by the CH3COOH is bound to urea and becomes &nbsp;electrochemically inactive which results in lowering of conventional dissociation constant of the acid. The altered <em>pK </em>values of acetic acid at 303K in different urea media are presented along with the percentage distribution of H⁺, UH⁺, Ac^- ions and the undissociated acetic acid (HAc). The results reveal the way urea can affect the transfer of proton from a weak acid to water by dissociation.