Water vapor tempera

Temperature (°C) Humidity (kg HjO/kg dry air) Water vapor partial pressure (kPa) Water vapor partial density (kg/m ) Water vaporization heat (kj/kg) Mixture enthalpy (kJ/kg dry air) Dry air partial density C gdryair mJ) Kinematic viscosity (lO m /s) Specific heat (kJ/K kg) Heat conductivity (W/m K) Diffusion factor v/ater ir (lOW/s) Tempera ( C)... 

At 25 °C, water is ordinarily a liquid. However, even at 25 °C, water evaporates. In a closed container at 25 °C, water evaporates enough to get a 27 torr water vapor pressure in its container. The pressure of the gaseous water is called its vapor pressure at that temperature. At different tempera-... 

An active volcano emits gases, hquids, and sohds. The gases spewed into the atmosphere include primarily N2, CO2, HCl, HF, H2S, and water vapor. It is estimated that volcanoes are the source of about two-thirds of the sulfur in the air. On the slopes of Mount St. Helens, which last erupted in 1980, deposits of elemental sttUrtr are visible near the eruption site. At high tempera-tmes, the hydrogen sulfide gas given off by a volcano is oxidized by air ... 

The thermal efficiency of a steam power cycle is increased when the press and hence the vaporization temperature in the boiler is raised. It is also increas by increased superheating in the boiler. Thus, high boiler pressures and te peratures favor high efficiencies. However, these same conditions increase capital investment in the plant, because they require heavier construction more expensive materials of construction. Moreover, these costs increase ev more rapidly as more severe conditions are imposed. Thus, in practice po plants seldom operate at pressures much above 10,000 kPa and tempera much above 600°C. The thermal efficiency of a power plant increases as pressure and hence the temperature in the condenser is reduced. However, condensation temperature must be higher than the temperature of the coo medium, usually water, and this is controlled by local conditions of climate geography. Power plants universally operate with the condenser pressure as 1 as practicable. 

Athanase Dupr was the first to propose representing by such a formula the relation which exists between the tension of saturated vapor of water or of any other liquid and the tempera ture. 

At the temperatures where ordinarily the vaporization of liquids, such as water and alcohol, is observed we may admit that the states of false equilibria are so close to the states of veritable equilibria that they are practically indistinguishable whence, whatever are the temperatures of an enclosure containing a liquid and its vapor, the conditions in which the enclosure exists are those of the first case the final tension of the vapor in the enclosure will be the same as if the enclosure were wholly brought to the tempera-ature of its coldest point it is in the cold region that the liquid will be found wholly condensed this proposition constitutes one of the forms of Waites principle. 

Water also has a very high heat of vaporization. It takes 540 calories to change 1 g of liquid water at 100°C to a gas and even more, 603 cal/g, when the water is at 37°C, human body temperature. That is about twice the heat of vaporization of alcohol. As water molecules evaporate, the surface of the hquid cools because only the highest-energy (or "hottest") molecules leave as a gas. Only the "hottest" molecules have enough energy to break the hydrogen bonds that bind them to other water molecules. Indeed, evaporation of water molecules from the surfaces of lakes and oceans helps to maintain stable tempera-... 

Combustible liquid flash point (closed cup) 54°C (130°F), (open cup) 68 C (155°F) vapor pressure 31 torr at 25°C (77°F) vapor density 2.5 (air = 1) autoignition tempera-tnre 360°C (680°F). Vapors of acrylic acid form explosive mixtures with air within the range 2.9-8.0% by volume in air. Fire-extingnishing agent water spray, alcohol foam, dry chemical, or CO2 nse a water spray to flnsh and dilute the spill and to disperse the vapors. 

Flammable liquid flash point (open cnp) 13°C (55°F) vapor density 3 (air = 1) the vapor can travel some distance to an ignition sonrce and flashback antoignition tempera-tnre 450°C (842°F) fire-extinguishing agent alcohol foam a water spray can be nsed to flnsh and dilnte the spill. Diethyl ketone forms explosive mixtnres with air the FEE valne is 1.6% by volnme of air, the UEL valne is not reported. 

Direct experimental proof that the true driving force for diffusive transport is the gradient of chemical potential rather than the concentration gradient is provided by the experiments of Haase and Siry who studied diffusion in binary liquid mixtures near the consolute point. At the consolute point the chemical potential (and the vapor pressure) are independent of composition so, according to Eq. (5.6), the diffusivity should be zero. The consolute point for the system n-hexane-nitrobenzene occurs at 20 C at a mole fraction 0.422 of nitrobenzene. The system shows complete miscibility above this temperature and forms two separate phases at lower temperatures. Opposite behavior is shown by the system water-triethylamine, for which the consolute tempera-... 

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