Question

A sample containing 42.8 g of Ar is enclosed in a container of volume 8.11×10⁻² L at 375 K.

Calculate P using the Redlich-Kwong equation of state

Answer 1

the gas is argon

Volume = 8.11 X 10^-2

Temperature = 375 K

Mass = 42.8 , so moles = mass / atomic weight = 42.8 / 40 = 1.07

According to Redlich =kwong equation of state

Vm = molar volume = volume / moles of gas = 8.11X 10^-2 / 1.07 = 7.58 X 10^-2

T = 375 K

Tc = critical temperature = −122.4 °C (150.8 K)

Pc = critical pressure = 48.1 atm (4,870 kPa)

a = 0.42748 R^2 Tc^2.5 / Pc = 0.42748 X (0.0821)^2 (150.8)^2.5 / 48.1 = 5.99 X 10^-5 X 279256.54

a = 16.712

b = 0.08664 RTc / Pc = 0.08664 X 0.0821 X 150.8 / 48.1 = 0.0223

Pressure = (30.7875 / 0.0535 )- (16.712 / 0.0758 X 0.0991 X 19.3649)

Pressure = 575.467 - 144.887 = 430.58 Atm