6. Determine the mass and the weight of the air contained in a room whose dimensions are 6 m _ 6 m _ 8 m. Assume thedensity of the air is 1.16 kg/m3.9. The constant-pressure specific heat of air at 25C is 1.005 kJ/kg C. Express this value in kJ/kg-K. J/g C, kcal/kg-C, and Btu/lbm-F.

13. A 4-kW resistance heater in a water heater runs for 2 hours to raise the water temperature to the desired level.Determine the amount of electric energy used in both kWh and kJ.

38. The temperature of water changes by 10F during a process. Express this temperature change in Celcius (C), Kelvin (K), and Rankine (R) units.

49. The water in a tank is pressurized by air, and the pressure is measured by a multifluid manometer as shown inFig. Pl-53. Determine the gage pressure of air in the tank if /;, = 0.2 m, h2 = 0.3 m, and h3 = 0.46 m. Take the densitiesof water, oil, and mercury to be 1000 kg/m3, 850 kg/m3, and 13,600 kg/m3, respectively.

54. The diameters of the pistons shown in Fig. P1-58E are Dj = 3 in and D2 = 1.5 in. Determine the pressure inchamber 3, in psia, when the other pressures are /', = 150 psia and P2 = 250 psia.

63. A gas is contained in a vertical, frictionless piston-cylinder device. The piston has a mass of 3.2 kg and a cross-sectional area of 35 cm2. A compressed spring above the piston exerts a force of 150 N on the piston. If the atmospheric pressure is 95 kPa, determine the pressure inside the cylinder.

79. The gage pressure of the air in the tank shown in Fig. PI-83 is measured to be 80 kPa. Determine the differentialheight h of the mercury column.