How many pounds of propane,C3H8, if you pay $20 for a 15L cylinder, filled to 150 psi at 25 degrees C.
Use the Ideal Gas Law to get the moles, n, or propane:
PV=nRT
Convert the 150 PSI to atm (1 atm = 14.7 psi)
Convert deg C to deg K (K = C + 273)
R = 0.0821 L.atm/K.mol
Substitute and solve for n (moles)
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Convert the moles to grams (1 mole C3H8 = 44.09g)
Convert the grams to lbs (1 lb = 454g)