Mixtures of Gases, Vapors, and Liquids Flashcards
Mass Fraction (Gravimetric or Weight Fraction)
The mass fraction is the ratio of the component’s mass to the total mass of the mixture. The sum of all the mass fractions is always equal to one.
Mole Fraction
The mole fraction is the ratio of the number of moles of that substance to the total number of moles of all the substances in the mixture. The mole fraction of a mixture of non reacting ideal gases is equal to the partial pressure ratio and volumetric fraction. The sum of all the mole fractions is always equal to one.
Molecular Weight
The molecular weight is the mass per mole of a component. It is used to convert mass fraction to mole fraction and vice versa.
Partial Pressure
The pressure a gas component would alone exert in the total volume at the temperature of a mixture of non reacting gases. (Ideal Gas Law)
Dalton’s Law
The total pressure of a gas mixture is the sum of the partial pressures.
Partial Volume
The volume a gas component would alone occupy, at the temperature and pressure of a mixture of non reacting gases. (Ideal Gas Law)
Amagat’s Law
The total volume of a mixture of non reacting gases is equal to the sum of the partial volumes.
Ideal Gas Mixtures
For mixtures of non reacting ideal gases, the mole fraction, partial pressure ratio, and volumetric fraction are the same.
Gibbs Theorem
States that the total property of a mixture of ideal gases is the sum of the properties that the individual gases would have if each occupied the total mixture volume alone at the same temperature. The total entropy requires the mixing of components to be isentropic and each components entropy must be evaluated at the temperature of the mixture and its partial pressure.
Henry’s Law
States that the partial pressure of a slightly soluble gas above a liquid is proportional to the amount (mole fraction) of the gas dissolved within the liquid. This law applies separately to each gas to which the liquid is exposed, as if each gas were present alone. It is important to recognize that (h) is Henry’s Law constant with units of pressure, (x) is the mole fraction of the gas solute in the liquid solvent, while (y) is the mole fraction of the gas solute in the gas mixture above the liquid.
Vapor Pressure
The vapor pressure is the pressure exerted by the solvent’s vapor molecules when they are in equilibrium with the liquid. Vapor pressure increases with increasing temperature.
Raoult’s Law
According to Raoult’s Law, the partial pressure of a solution component will increase with increasing temperature and with increasing mole fraction of that component in the solution. This law applies to each of the substances in the solution.
Psychometrics
Psychometrics is the study of the properties and behavior of atmospheric air.
Atmospheric Air
Atmospheric air contains small amounts of moisture and can be considered to be a mixture of two ideal gases, dry air and water vapor. All of the thermodynamic rules relating to the behavior of non reacting gas mixtures apply to atmospheric air.
Total Atmospheric Pressure
The total atmospheric pressure is equal to the sum of the dry air partial pressure and water vapor partial pressure.
Dry Bulb Temperature
The temperature that a regular thermometer measures if exposed to air.
Wet Bulb Temperature
The temperature of air that has gone through an adiabatic saturation process. It is measured with a thermometer that is covered with a water saturated cotton wick.
Dew Point Temperature
This is the dry bulb temperature at which water starts to condense when moist air is cooled in a isobaric process. The dew point temperature is equal to the saturation temperature for the partial pressure of the vapor.
Saturation Pressure
For every temperature, there is a unique equilibrium vapor pressure of water called the saturation pressure. If the vapor pressure equals the saturation pressure, the air is said to be saturated.
Saturated Air
Saturated air is a mixture of dry air and water vapor at the saturation pressure. When the air is saturated, all three temperatures are equal.
Unsaturated Air
Unsaturated air is a mixture of dry air and superheated water vapor. When the air is unsaturated, the dew point temperature is lower than the wet bulb temperature, and the wet bulb temperature is lower than the dry bulb temperature.
Specific Humidity (Humidity Ratio)
The humidity ratio is equal to the mass ratio of water vapor to dry air and it specifies the amount of water in atmospheric air. The partial pressure can also be used to obtain the humidity ratio.
Relative Humidity
The relative humidity is the partial pressure of the water vapor divided by the saturation pressure at the dry bulb temperature.
Psychometric Chart
Psychometric chart is used by specifying the values of any two parameters on intersecting scales. Once the state has been located on the chart, all other properties can be read directly.
Enthalpy of Dry Air
Enthalpy of an air vapor mixture is the sum of the enthalpy of dry air plus the product of the enthalpy of the water vapor and humidity ratio. This computes the enthalpy per pound of dry air. In psychometrics, the basis for the total enthalpy of air (an air water vapor mixture) is the mass of the dry air only not the total air mass.
