The Soave-Redlich-Kwong (SRK) equation is a commonly used equation of state that

Question

The Soave-Redlich-Kwong (SRK) equation is a commonly used equation of state that relates the absolute temperature T, the absolute pressure P, and the molar volume V of a gas under conditions in which the behavior of the gas cannot be considered ideal. Where R is the ideal gas constant and theta, a, and b, are parameters specific to the gas, calculated as : a=0.42747(RTc)^2/Pc , b=0.08664RTc/Pc , m=0.48508+1.55171w-0.1561w^2 , Tr=T/Tc , theta= [1+m(1-square root of Tr)]^2 . Here, Tc is the critical temperature of the gas, Pc is the critical pressure of the gas, and w is the Pitzer acentric factor. Each of these is readily available for many gases. Calculate the pressure exerted by 20 gram-moles of ammonia at 300 k in a 5 liter container, using a. the ideal gas equation , b. the SRK equation. The required data for ammonia are tabulated as follows: Tc=405.5K, Pc=111.3atm, w=0.25

Explanation / Answer

a) Molar mass of Ammonia (NH3) = 1 * 14 + 3 * 1 = 17 gm/mol

Number of moles of ammonia = 20/17 = 1.17647 moles

using ideal gas equation

PV = nRT

P(5) = 1.17647 * 0.0821 * 300

P = 5.795 atm

b) P = RT/(Vm-b) - a*alpha/Vm(Vm+b)

The value of a and b is not given in the problem, hence we can't find the pressure of the gases using SRK equation

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