Problem 1. Calculate the work involved in expanding

Calculate the work involved in expanding 20.0 L of an ideal gas to a final volume of 85.0 L against a constant external pressure of 2.50 bar.
 
Solution: 
 
$W_{irr}=-P_{ext}\Delta V=-2.5\;barx\frac{100000\;Pa}{1\;bar}(85-20)Lx\frac{1\;m^3}{1000\;L}=-16300\;J$