Vapor pressure of pure water

A solution contains 82.0 g of glucose, QH Oe, in 322 g of water. Calculate the vapor pressure lowering at 25°C (vapor pressure of pure water =... 

Seif-Test 8.11A Calculate the vapor pressure of water at 90.°C for a solution prepared by dissolving 5.00 g of glucose (C6H1206) in 100. g of water. The vapor pressure of pure water at 90.°C is 524 Torr. 

CH,CH(CN)—. (c) What would be the vapor pressure of the solution if the vapor pressure of pure water at 25°C is 0.0313 atm (Assume that the density of the solution is 1.00 g-ern .) (d) Which approach (osmometry or the lowering of vapor pressure) would you prefer for the determination of very high molar masses such as those of acrylic resins Why ... 

A closed bottle contains vinegar, which is 5.0% by mass acetic acid in water. Calculate the vapor pressure of water above the vinegar at 25 °C. The vapor pressure of pure water at 25 °C is 23.76 torr. 

The vapor pressure of pure water under these conditions is 23.76 torr. Any nonvolatile solute reduces the vapor pressure, so we expect a result that is smaller than this value. 

C12-0063. Urea, a fertilizer, has the chemical formula (NH2)2 CO. Calculate the vapor pressure of water above a fertilizer solution containing 7.50 g of urea in 15.0 mL of water (density = l.OOg/mL), at a temperature for which the vapor pressure of pure water is 33.00 torr. 

Figure 2.4 shows the equilibrium relationships of biological materials between the water content and the water activity, at constant temperatures and pressures. These data were first published in 1971, but did not find much attention in the RM field until now. At equilibrium the water activity is related to the relative humidity cp of the surrounding atmosphere (Equation 2.3) where p is the equihbrium water vapor pressure exerted by the biological material and po the equilibriiun vapor pressure of pure water at the same temperature. 

At 100°C, the boiling point of water, the vapor pressure of pure water, Plater = 760 torr. 

The approximate relative humidity then will be 90% (90.04 %), because the water vapor pressure above the NaCl saturated solution will be 90.04% of the vapor pressure of pure water at 20° C. 

Because the chemical potentials of water distributed in two phases (i.e., solution and vapor) must be equal, the water activity of a food can be measured by bringing the food into equilibrium with the air above it. At equilibrium, under conditions of constant temperature and pressure, the aw values of the aqueous phase of a food (aw l) and of the air (aw v) are equal and can be estimated from the ratio of the partial vapor pressure of water above the food (pv) to the vapor pressure of pure water (p") at the same temperature (Walstra, 2003) ... 

The pressure-temperature-composition diagram presented by Morey is shown in Fig. 8. The vapor pressure of pure water (on the P-T projection) terminates at the critical point (647 K, 220 bar). The continuous curve represents saturated solutions of NaCl in water, i.e., there is a three-phase equilibrium of gas-solution-solid NaCl. The gas-phase pressure maximizes over 400 bar at around 950 K. Olander and Liander s data for a 25 wt. % NaCl solution are shown, and T-X and P X projections given. At the pressure maximum, the solution phase contains almost 80% NaCl. 

What would be the proper setup to determine the vapor pressure of a solution at 25°C that has 45 grams of C6H12O6, glucose (MM = 180 g mol ), dissolved in 72 grams of H2O The vapor pressure of pure water at 25°C is 23.8 torr. 

Relative Humidity ratio of the vapor pressure of water in air compared to the saturated vapor pressure of pure water at the same temperature, measure of the amount of water vapor in an air mass expressed as percent of how much water vapor that air mass can hold Relative Mass mass measured with respect to a standard, atomic masses based on C-12 standard... 

Use the Kelvin equation (Chapter 14.C.2) to show that it is true that the vapor pressure of pure water at 25°C is only 0.1% greater over a l-/u,m radius particle than over a flat surface, but 11% greater over a 0.01-/zm radius particle. The surface tension of water is 72 dyn cm 1 at 25°C. 

The upper ends of the isobars on Figures 16-18 and 16-19 terminate at the vapor pressure of pure water at each temperature. Liquid water ceases to exist at pressures below the end of each line. 

Figure A2.1.2 Effect of temperature on vapor pressure measurement. The upper curve is the vapor pressure of pure water, pw°. The lower curve is a system whose partial water vapor pressure, pw, is always a constant fraction of the vapor pressure of pure water. See text for details.

The influence of temperature on the measurement is best illustrated by referring to Figure A2.1.2. Here, the upper curve represents the vapor pressure of pure water, pw°, as a function of temperature, and the lower curve represents a system whose partial water vapor pressure is always a constant fraction, a, of the vapor pressure of pure water. The points E and G representpw° at temperatures T and T2, respectively. The points F and H represent pw at temperatures 7 , and T2, respectively. At both Tx and T2, the ratio of the vapor pressures [pw/pw°]r is a (i.e., the ratios of the lines BF/BE and the lines DH/DG are both equal to a). 

Water activity, a thermodynamic property, is defined as the ratio of the vapor pressure of water in a system to the vapor pressure of pure water at equal temperature, or the equilibrium relative humidity of the air surrounding the system at equal temperature. 

The vapor pressure of water absorbed on silica gel can be expressed as a function of the vapor pressure of pure water for various gel loadings in spacecraft humidity-water-recovering systems. For the water loading of 0.1 lb water/lb dry silica gel, the following data were obtained ... 

For example, we can calculate the vapor pressure of a 5.0% (by mass) sucrose solution at 45°C. At this temperature, the vapor pressure of pure water is 71.9 torr. Since sugar is essentially nonvolatile, we have to concern ourselves only with the vapor pressure of the water. 

Our study also investigated the effect of water activity (a ) on the kinetics of the formation of pyrazines. water activity is defined as the ratio of partial pressure of water in a food to the vapor pressure of pure water at a given temperature. Nonfat dry milk (NFEM) was chosen as a model system for this study since NFEM and lactose/casein systems which had undergone nonenzymatic browning were found to contain pyrazines (21. 22). The current study investigates the effect of increasing product over the range of 0.32 to 0.85 on the rate of formation of pyrazines. 

Glucose, C6H1206, is commonly mixed with water to make intravenous feeding solutions. What would be the vapor pressure of a solution where 60.0 g of glucose (molar mass 180.16 g) is dissolved in 700.0 g HzO at 22°C The vapor pressure of pure water at 22°C is 19.83 mm Hg. 

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