Quimica

1.1 MOLAR GAS CONSTANT
Calculate the molar gas constant R in the following units:
a. (atm)(cm3)/(g · mol)(K)
b. (psia)(ft3)/(lb· mol)(◦R)
c. (atm)(ft3)/(lb · mol)(K)
d. kWh/(lb · mol)(◦R)
e. hp · h/(lb · mol)(◦R)
f. (kPa)(m3)/(kg · mol)(K)
g. cal/(g ·mol)(K)
Calculation Procedure
1. Assume a basis. Assume gas is at standard conditions, that is, 1 g · mol gas at 1 atm (101.3 kPa)pressure and 0◦C (273 K, or 492◦R), occupying a volume of 22.4 L.
2. Compute the gas constant. Apply suitable conversion factors andobtain the gas constant in
various units. Use PV = RT; that is, R = PV /T . Thus,
a. R = (1 atm)[22.4 L/(g · mol)](1000 cm3/L)/273 K = 82.05 (atm)(cm3)/(g · mol)(K)
b. R = (14.7 psia)[359 ft3 /(lb · mol)]/492◦R = 10.73 (psia)(ft3)/(lb · mol)(◦R)
c. R = (1atm)[359 ft3 /(lb · mol)]/273 K = 1.315 (atm)(ft3)/(lb · mol)(K)
d. R =[10.73 (psia)(ft3)/(lb · mol)(◦R)](144 in2 /ft2)[3.77×10−7kWh/(ft · lbf)]=5.83×10−4 kWh/
(lb · mol)(◦R)
e. R = [5.83 × 10−4 kWh/(lb · mol)(◦R)](1/0.746 hp · h/kWh) = 7.82 × 10−4 hp · h/(lb ·mol)(◦R)
f. R = (101.325 kPa/atm)[22.4 L/(g · mol)][1000 g · mol/(kg · mol)]/(273 K)(1000 L/m3) =
8.31 (kPa)(m3)/(kg · mol)(K)
g.R = [7.82 × 10−4 hp · h/(lb · mol)(◦R)][6.4162 × 105 cal/(hp · h)][1/453.6 lb · mol/(g · mol)]
(1.8◦R/K) = 1.99 cal/(g · mol)(K)