Pressure of Water at Various Temperatures

Consider a sealed flask with a movable piston that contains 5.25 L of 02 saturated with water vapor at 25°C. The piston is depressed at constant temperature so that the gas is compressed to a volume of 2.00 L. (Use the table in Appendix 1 for the vapor pressure of water at various temperatures.)... 

The vapor pressure of water at various temperatures is given in Table 8.3. (a) What is the relative humidity at 30.°C when the partial pressure of water is 25.0 Torr (b) Explain what would be observed if the temperature of the air were to fall to 25°C. 

See Chapter 5 for information about vapor pressure. The vapor pressure of water at various temperatures appears in Table. 

Table 12.3 Vapor Pressure of Water at Various Temperatures ...

The curved line from T to C in Figure 13-17a is a vapor pressure curve obtained experimentally by measuring the vapor pressures of water at various temperatures (Table 13-8). Points along this curve represent the temperature-pressure combinations for which liquid and gas (vapor) coexist in equilibrium. At points above AC, the stable form of water is liquid below the curve, it is vapor. 

Figure 10.12 shows the saturated vapour pressure of water at various temperatures. The figure also shows the way that the saturated vapour pressure of ethanol varies with temperature. The vapour pressure of water and ethanol (like that of all liquids) increases with temperature. This is expected, since at the higher temperature more liquid molecules have sufficient energy to escape the attractive forces holding molecules in the liquid. 

The physical properties of light water (H O), heavy water (D O) and superheavy water (T O) at room temperature (20°C) are listed in Table 20.14, while polynomial equations for calculating the density, viscosity, surface tension and vapor pressure of water at various temperature are provided in Table 20.15. 

As Figure 11.7 demonstrates, the vapor pressure of a substance depends on the temperature. (Appendix B gives a table of the vapor pressures of water at various temperatures.) As the temperature increases, the kinetic energy of molecular motion becomes greater, and the vapor pressure increases. Liquids and solids with relatively high vapor pressure at normal temperatures arc said to be volatile. Chloroform and carbon tetrachloride are volatile liquids. Naphthalene, CioHg, and para-dichlorobenzene, C6H4CI2, are volatile solids they have appreciable vapor pressures at room temperature. Both arc used to make mothballs. 

By subtracting the partial pressure of water from the total pressure, which is equal to atmospheric pressure, we can determine the partial pressure of oxygen—and thereby determine how many moles are produced by the reaction. We get the partial pressure of water, which depends on temperature, from a table of values. Table 11.5 lists the partial pressure (also known as the vapor pressure) of water at various temperatures. 

The experimental values of the solvation Gibbs energies of water in water are obtainable from the densities of the liquid and the vapor pressure of water at various temperatures. It is assumed that the vapor at equilibrium with liquid water at most temperatures of interest may be viewed as ideal gas, in which we have (see section 6.13)... 

When liquid molecules with sufficient kinetic energy break away from the surface, they become gas particles or vapor. In an open container, all the liquid will eventually evaporate. In a closed container, the vapor accumulates and creates pressure called vapor pressure. Each liquid exerts its own vapor pressure at a given temperature. As temperature increases, more vapor forms, and vapor pressure increases. Table 11.4 lists the vapor pressure of water at various temperatures. 

Exercise 16.4. The following data give the vapor pressure of water at various temperatures. Transform the data, using In (P) for the dependent variable and 1/T for the independent variable. Carry out the linear least-squares fit by hand, calculating the four sums. Find the molar enthalpy change of vaporization. 

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