Enthalpy of combustion of acetylsalicylic acid

✍ Scribed by Duane R. Kirklin

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 92 KB
• Volume: 32
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.1999.0650

✦ Synopsis

The massic energy of combustion of crystalline acetylsalicylic acid was determined in an NIST adiabatic-aneroid-rotation bomb calorimeter. The standard molar enthalpy of combustion at T = 298.15 K and p o = 10 5 Pa is c H o m (C 9 H 8 O 4 , cr, 298.15 K) = -(3926.71 ± 0.34) kJ • mol -1 . The derived standard molar enthalpy of formation is f H o m (C 9 H 8 O 4 , cr, 298.15 K) = -(758.19 ± 0.52) kJ • mol -1 . The molar enthalpy of fusion fus H o m (C 9 H 8 O 4 , cr, 414.0 K) = (29.80± 0.22) kJ • mol -1 was determined by differential scanning calorimetry. The molar Kirchhoff relationship, d( H ) = C p dT , was used to convert this value to T = 298.15 K, fus H o m (C 9 H 8 O 4 , cr, 298.15 K) = (19.28 ± 0.22) kJ • mol -1 . The molar enthalpy of vaporization was estimated using the group contribution scheme of Lebedev and Miroshnichenko. The molar enthalpy of vaporization of acetylsalicyclic acid was estimated as vap H o m (C 9 H 8 O 4 , cr, 298.15 K) = (106.4 ± 2.0) kJ • mol -1 . The molar enthalpies of fusion and vaporization were used to calculate enthalpies of formation for the liquid and gaseous states of acetylsalicyclic acid, f H o m (C 9 H 8 O 4 , l, 298.15 K) = -(738.91 ± 0.56) kJ • mol -1 and f H o m (C 9 H 8 O 4 , g, 298.15 K) = -(632.5 ± 2.1) kJ • mol -1 , respectively.