Two pounds of air contained in a cylinder expand without friction against a piston. The pressure on the back side of the piston is constant at 200 psia. The air initially occupies a volume of 0.5 ft3. What is the work done by the air in ft-lbf if the expansion continues until the temperature of the air reaches 100 F?
Q - W = m(uf - ui), which translates to W = m*cv*(Tf - Ti) [Q is 0 because there's no heat transfer]
PV = mRT
The Attempt at a Solution
W = 2 lbm (0.171 Btu/lbm R)(559.67 R - Ti)
The text says the answer is 45300 ft-lbf
Basically I don't really know how to start this all off. I know I need to find the initial temperature which I think means I need to use PV = mRT but I can't find an agreeable R value in my book (also I have no idea if my cv value is correct). Could someone just point me in the right direction?