Dissociation quotient of benzoic acid in aqueous sodium chloride media to 250{degrees}C
- Univ. of Nebraska, Lincoln, NE (United States)
- Oak Ridge National Lab., TN (United States)
The dissociation quotient of benzoic acid was determined potentiometrically in a concentration cell fitted with hydrogen electrodes. The hydrogen ion molality of benzoic acid/benzoate solutions was measured relative to a standard aqueous HCl solution at seven temperatures from 5 to 250{degrees}C and at seven ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The molal dissociation quotients and selected literature data were fitted in the isocoulombic (all anionic) form by a six-term equation. This treatment yielded the following thermodynamic quantities for the acid dissociation equilibrium at 25{degrees}C and 1 bar: logK{sub a} = -4.206{+-}0.006, {Delta}H{sub a}{sup 0} = 0.3{+-}0.3 kJ-mol{sup {minus}1}, {Delta}S{sub a}{sup 0} = -79.6{+-}1.0 J-mol{sup {minus}1}-K{sup {minus}1}, and {Delta}C{sub p;a}{sup 0} = -207{+-}5 J-mol{sup {minus}1}-K{sup {minus}1}. A five-term equation derived to describe the dependence of the dissociation constant on solvent density is accurate to 250{degrees}C and 200 MPa.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 70284
- Journal Information:
- Journal of Solution Chemistry, Journal Name: Journal of Solution Chemistry Journal Issue: 4 Vol. 24; ISSN JSLCAG; ISSN 0095-9782
- Country of Publication:
- United States
- Language:
- English
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