Question

A cylinder of 10-m-high, and a cross-sectional area of 0.1 m2 , has a piston (that is free to move) assumed to have negligible mass and thickness (see Figure 1(a)). Above the piston there is a liquid that is incompressible (constant density and volume) with ρliquid = 1000 kg/m3 . Below the piston there is air at 300 K, with a volume of 0.3 m3 . Assume air is an ideal gas (Ru =8.314 J.mol-1 .K-1 ; Mair = 28.9628 g/mol) Use P0 = 101.325 kPa and g = 9.807 m/s2 Find the following: a- The mass (in kg) of the liquid in the cylinder. b- The initial pressure of the air compartment. c- The initial mass of air (in kg). d- The initial internal energy of air. Another negligible mass and thickness piston is placed on top of the cylinder (see Figure 1b) and pushed down by 0.1 m to compress the air. The process is isothermal. The liquid is incompressible (its volume and phase do not change). Calculate: e- The final volume of air. f- The final temperature of air when thermal equilibrium is obtained. g- The final pressure of air. h- Does the internal energy of air change? i- The boundary work used to lower the piston located on top of the air. j- The total heat transfer outside of the piston from the air compartment.

Answer 1