A barometer lube 88 cm long contains some air above the merc

A barometer lube 88 cm long contains some air above the mercury. It gives a reading of 68 cm when upright. When the tube is tilted to an angle of 45 degree, the length of the mercury column becomes 80 cm. Which of the following most nearly equals the reading of an accurate barometer? 76.0 mm Hg 75.8 mm Hg 75.6 mm Hg 75.2 mm Hg Which of the following most nearly equals the resulting quality of the steam if 5.0 kg of water is injected into an evacuated vessel that is maintained at 175 degree C, if the volume of the vessel is 283 1? 26% 32% 21% 35%

Solution

1.26

From steam tables, at 175 deg C we have v_liq = 0.00112 m^3/kg and v_vap = 0.217 m^3/kg

For the mixture we have specific volume v = V/m = 283*10^-3 / 5 = 0.0566 m^3/kg

Now, Quality x= (v - v_liq) / (v_vap - v_liq)

x = (0.0566 - 0.00112) / (0.217 - 0.00112)

x = 0.257 or 25.7%