Temperature dependence of dissociation constants for formic acid and 2,6-dinitrophenol in aqueous solutions up to 175°C

Myung Hwa Kim, Chang Shik Kim, Haeng Woo Lee, Keon Kim

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

The temperature dependence of the dissociation constants for formic acid and 2,6-dinitrophenol (2,6-DNP) has been determined in aqueous solutions from 25 to 175°C using spectrophotometric measurements. The optical indicator 2,6-DNP was employed to measure the pH of a buffer solution by deconvolution of absorption spectra of 2,6-DNP at various temperatures. First, using the temperature dependence of pKa for acetic acid, pKi of 2,6-DNP were determined in acetate buffer solutions as a function of temperature. The results were then used to study the ionization reaction of formic acid at elevated temperature. Measured values of pKa for formic acid were fitted to a function of temperature, which was derived by assuming that ΔC°p is a non-zero constant. The result for formic acid was given by pKa = -57.528 + 2773.9/T + 9.1232 In T where T is absolute temperature. Additionally, thermodynamic functions of formic acid were determined from the temperature dependence of pKa and compared with those obtained from other methods. The isocoulombic reactions for formic acid and 2,6-DNP were considered to predict the temperature dependence of pKa by the extrapolation of -log KOH values to higher temperatures.

Original languageEnglish
Pages (from-to)4951-4956
Number of pages6
JournalJournal of the Chemical Society - Faraday Transactions
Volume92
Issue number24
Publication statusPublished - 1996 Dec 21

Fingerprint

formic acid
dissociation
aqueous solutions
temperature dependence
Temperature
buffers
temperature
Buffers
acetic acid
2,6-dinitrophenol
extrapolation
acetates

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Temperature dependence of dissociation constants for formic acid and 2,6-dinitrophenol in aqueous solutions up to 175°C. / Kim, Myung Hwa; Kim, Chang Shik; Lee, Haeng Woo; Kim, Keon.

In: Journal of the Chemical Society - Faraday Transactions, Vol. 92, No. 24, 21.12.1996, p. 4951-4956.

Research output: Contribution to journalArticle

@article{768cf1e411e4446e8c134e3c7e6fe247,
title = "Temperature dependence of dissociation constants for formic acid and 2,6-dinitrophenol in aqueous solutions up to 175°C",
abstract = "The temperature dependence of the dissociation constants for formic acid and 2,6-dinitrophenol (2,6-DNP) has been determined in aqueous solutions from 25 to 175°C using spectrophotometric measurements. The optical indicator 2,6-DNP was employed to measure the pH of a buffer solution by deconvolution of absorption spectra of 2,6-DNP at various temperatures. First, using the temperature dependence of pKa for acetic acid, pKi of 2,6-DNP were determined in acetate buffer solutions as a function of temperature. The results were then used to study the ionization reaction of formic acid at elevated temperature. Measured values of pKa for formic acid were fitted to a function of temperature, which was derived by assuming that ΔC°p is a non-zero constant. The result for formic acid was given by pKa = -57.528 + 2773.9/T + 9.1232 In T where T is absolute temperature. Additionally, thermodynamic functions of formic acid were determined from the temperature dependence of pKa and compared with those obtained from other methods. The isocoulombic reactions for formic acid and 2,6-DNP were considered to predict the temperature dependence of pKa by the extrapolation of -log KOH values to higher temperatures.",
author = "Kim, {Myung Hwa} and Kim, {Chang Shik} and Lee, {Haeng Woo} and Keon Kim",
year = "1996",
month = "12",
day = "21",
language = "English",
volume = "92",
pages = "4951--4956",
journal = "Physical Chemistry Chemical Physics",
issn = "1463-9076",
publisher = "Royal Society of Chemistry",
number = "24",

}

TY - JOUR

T1 - Temperature dependence of dissociation constants for formic acid and 2,6-dinitrophenol in aqueous solutions up to 175°C

AU - Kim, Myung Hwa

AU - Kim, Chang Shik

AU - Lee, Haeng Woo

AU - Kim, Keon

PY - 1996/12/21

Y1 - 1996/12/21

N2 - The temperature dependence of the dissociation constants for formic acid and 2,6-dinitrophenol (2,6-DNP) has been determined in aqueous solutions from 25 to 175°C using spectrophotometric measurements. The optical indicator 2,6-DNP was employed to measure the pH of a buffer solution by deconvolution of absorption spectra of 2,6-DNP at various temperatures. First, using the temperature dependence of pKa for acetic acid, pKi of 2,6-DNP were determined in acetate buffer solutions as a function of temperature. The results were then used to study the ionization reaction of formic acid at elevated temperature. Measured values of pKa for formic acid were fitted to a function of temperature, which was derived by assuming that ΔC°p is a non-zero constant. The result for formic acid was given by pKa = -57.528 + 2773.9/T + 9.1232 In T where T is absolute temperature. Additionally, thermodynamic functions of formic acid were determined from the temperature dependence of pKa and compared with those obtained from other methods. The isocoulombic reactions for formic acid and 2,6-DNP were considered to predict the temperature dependence of pKa by the extrapolation of -log KOH values to higher temperatures.

AB - The temperature dependence of the dissociation constants for formic acid and 2,6-dinitrophenol (2,6-DNP) has been determined in aqueous solutions from 25 to 175°C using spectrophotometric measurements. The optical indicator 2,6-DNP was employed to measure the pH of a buffer solution by deconvolution of absorption spectra of 2,6-DNP at various temperatures. First, using the temperature dependence of pKa for acetic acid, pKi of 2,6-DNP were determined in acetate buffer solutions as a function of temperature. The results were then used to study the ionization reaction of formic acid at elevated temperature. Measured values of pKa for formic acid were fitted to a function of temperature, which was derived by assuming that ΔC°p is a non-zero constant. The result for formic acid was given by pKa = -57.528 + 2773.9/T + 9.1232 In T where T is absolute temperature. Additionally, thermodynamic functions of formic acid were determined from the temperature dependence of pKa and compared with those obtained from other methods. The isocoulombic reactions for formic acid and 2,6-DNP were considered to predict the temperature dependence of pKa by the extrapolation of -log KOH values to higher temperatures.

UR - http://www.scopus.com/inward/record.url?scp=33748595286&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33748595286&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:33748595286

VL - 92

SP - 4951

EP - 4956

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9076

IS - 24

ER -