Question

A low pressures, the van der Waals equation is written as:

$(P+\frac{a}{V^2})V=RT$

The compressibility factor is then equal to:

• A. $(1-\frac{a}{RTV})$
• B. $(1-\frac{RTV}{a})$
• C. $(1+\frac{a}{RTV})$
• D. $(1+\frac{RTV}{a})$

Answer 1

The correct option is A $(1-\frac{a}{RTV})$

$(P+\frac{a}{V^2})V=RT$
$PV+\frac{a}{V}=RT;\frac{PV}{RT}+\frac{a}{RTV}=1$
$\frac{PV}{RT}=Z$ (compressibility factor)
$Z=1-\frac{a}{RTV}$