Two cubic feet of air at atmospheric pressure is compressed to 0.50 ft3. For isothermal conditions what is the final pressure? What would be the final pressure if no heat were lost during compression?

A spherical balloon filled with H2 gas to a volume of 3.35x10-2 m3 at 17 °C is carefully lowered into the sea to a depth of 50 m, where the seawater temperature is about 12 °C.  Assume the gas is always in thermal equilibrium with the surrounding seawater.  The atmospheric pressure at the surface is P0 = 1.013 x 105 N/m2 and the specific gravity of the seawater is 1.03.      What is the change in thermal energy of the gas from surface to 50 m below?

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Determine the mass (ibm) of air in a classroom that is 30 ft wide, 50 ft long, and 15 ft high. The pressure is 14.7 psia and the temperature is 70 F. Do not convert to Sl unites. Thank you!