Thermodynamics

Convert to SI units and do problems below:

1. A piston has an area of 1 ft². (a) What mass must the piston have if it exerts a pressure of 10 lbf/in² above the atmospheric pressure (i.e.  unit such as psig or psi gage) on the gas enclosed in the cylinder? Assume standard gravitational acceleration. (b) Assuming air and ideal gas, compute the density when the temperature is 20^o C. Equivalent molecular weight of air is 28.97 kg/kmol.

2. A pressure gage reads 40.7 lbf/in², and the barometer reads 29.2 in Hg. Calculate the absolute pressure in: lbf/in² , atm, N/m² and mmHg.

3. A spherical balloon has a radius of 10 ft. The atmospheric pressure is 14.7 lbf/in². and the temperature is 60 ^o F.

a) Calculate the mass and number of moles of air this balloon displaces.

b) If the balloon is filled with helium at 14.7 lb/in², 60^o F, what is the mass and the number of moles of helium?

4. A metal of sphere of 6 in inside diameter is weighed on a precision beam balance when evacuated and again when filled to 110 lbf/in² with an unknown gas . The difference in weight is 2.25 gm. The room temperature is 80^o F. What is the gas, assuming it to be a pure substance?