Answer
$e=-19.05\%$
Work Step by Step
$P_{R}=\frac{P}{P_{cr}}=\frac{7MPa}{7.39MPa}=0.947$
$T_{R}=\frac{T}{T_{cr}}=\frac{380K}{304.2K}=1.250$
From Fig. A-15:
$Z=0.84$
Knowing that: $\upsilon=Z\upsilon_{ideal}$
Then the error is:
$e=\frac{\upsilon-\upsilon_{ideal}}{\upsilon}=1-\frac{1}{Z}=1-\frac{1}{0.84}=-0.1905=-19.05\%$
