A tank of 50 ft^3 volume contains saturated ammonia at a
pressure of 200 lbf/in^2. Initially the tank contains 50% liquid
and 50% vapor by volume. Vapor is withdraw from the top of the
tank until the pressure is 100 lbf/in^2. Assuming that only
vapor (i.e., no liquid) leaves and that the process is
adiabatic, calculate the mass of ammonia withdrawn.   Detailed
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