6. Determine the mass and the weight of the air contained ina 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 25Cis 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 for2 hours to raise the water temperature to the desired level.Determine the amount of electric energy used in both kWhand kJ.

38. The temperature of water changes by 10F during aprocess. 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 pressureis 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, and13,600 kg/m3, respectively.

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

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

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