Question

What is the specific volume of air at 15 psia and 90F in ft^3/lb?

Answer 1

T=90 F = 549.67 °R

$p=15 \times 144 = 2160 \;lb/ft^2$

$R=1.554 \times 10^3$

Ideal gas law

$pV=RT \\ 2160V = \frac{1.554 \times 10^3}{28.67} \times 549.67 \\ V=13.79 \;ft^3/lb$