Spectrophotometric determination of dissociation constants for propionic acid and 2,5-dinitrophenol at elevated temperatures |
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Authors: | In-Ja Lee Gang-Sook Jung Keon Kim |
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Institution: | 1. Department of Chemistry, Dongguk University, 780-714, Kyongju, Korea 2. Department of Chemistry, Korea University, 136-701, Seoul, Korea
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Abstract: | Using the temperature dependence of pKa for acetic acid, the pKa for 2,5-dinitrophenol have been spectrophotometrically determined in acetate buffer at elevated temperatures under the saturation vapor pressures. For 2,5-dinitrophenol $$pK_a = - 33.206 + 2106.7/T + 5.495\ln T$$ where T is in Kelvin. Similarly, pKa values of propionic acid were obtained at temperatures from 25°C to 175°C producing $$pK_a = - 43.703 + 2128.6/T + 7.2686\ln T$$ From this result, several thermodynamic functions of propionic acid were calculated and compared with those obtained from emf measurement. |
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