University:
Boston University
Course:
CAS CH 101 | General Chemistry 1
Academic year:

2020
Views:

116

Pages:

1
Author:

Kamila Boyle

Molar gas constant Student: “Which value of the gas constant should I use?” Teacher: “Use R = 8.31446 J/(mol K) and then convert units as needed.” The currently accepted SI value of the molar gas constant as R = 8.31446 J mol K The gas constant can be expressed in terms of the SI unit of pressure bar using 1 J = 1 L kPa = 0.01 L bar, since 1 bar = 100 kPa, and it can be expressed in terms of the historical but now non-standard unit of pressure atm using 1 J = 0.01 L atm/1.01325, since 1 atm is defined as exactly 1.01325 bar. With these conversions, the molar gas constant can be expressed alternatively as the three different numerical values R = 8.31446 J  mol K = 0.0831446 L bar  mol K = 0.0820573 L atm mol K Rather than memorize these three different values of R, it is recommended instead to remember just the single SI value R = 8.31446 J  mol K, and then to use the conversions 1 J = 1 L kPa = 0.01 L bar and 1 atm = 1.01325 bar as needed.