The state characteristics of matter can be expressed as a state equation by a compression factor(Z). Water(H₂O) vaporizes at 99.61C and 0.1 MPa. Calculate the compression factor(Z) using the conditions and equations below. (Considering gas only)

Conditions: T=438.7, P=24.3MPa / T_c = 647.14K, P_c = 22.064MPa Equation: Z = Z⁽⁰⁾ + wZ⁽¹⁾ / w=0.344 I don't know how to calculate Z⁽⁰⁾ and Z⁽¹⁾.

And please tell me the definition of w(acentricity).