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1. Petroleum Industry
➢ Hydrocarbon Separation: Phase behavior of hydrocarbon mixtures is vital for processes such as natural gas processing, where phase equilibria determine the conditions for separating methane, ethane, propane, and other components.
➢ Enhanced Oil Recovery: Knowledge of phase equilibria helps in designing techniques for enhanced oil recovery, such as injecting gases or chemicals to alter the phase behavior of the oil, improving extraction efficiency.
2. Pharmaceuticals
➢ Drug Formulation: Phase equilibria information is used to optimize drug formulation and stability. Understanding the solubility and crystallization behavior of active pharmaceutical ingredients (APIs) in various solvents is key to developing effective drugs.
➢ Lyophilization (Freeze-Drying): This process involves freezing a product and then reducing the surrounding pressure to allow the frozen water to sublimate.
Phase equilibria of water play a critical role in determining the optimal conditions for freeze-drying pharmaceuticals.
3. Semiconductor Manufacturing
➢ Crystal Growth: Phase equilibria are crucial in the growth of single crystals, such as silicon, used in semiconductor devices. The conditions for melting and solidification must be carefully controlled to obtain high-purity, defect-free crystals.
Vapor Liquid Equilibria (VLE) involves the distribution of a chemical species between vapor and liquid phases. At equilibrium, temperature, pressure, and partial fugacities of individual components must be equal across all phases.
Vapor Liquid Equilibrium
Vapor pressure is the pressure exerted by a pure component in contact with its liquid at a given temperature. It is temperature-dependent and can be calculated using the Antoine Equation.
Liquids with higher vapor pressures (volatile liquids) have lower boiling points.
Vapor
Liquid
Effect of Temperature on Vapor Pressure of Liquids
When the temperature of the liquid increases, the average kinetic energy of the liquid particles increases. Higher temperature means particles move faster (higher kinetic energy). This increased movement allows more particles to escape from the liquid phase into the vapor phase.
The vapor pressure of a liquid is the pressure exerted by the vapor when it is in equilibrium with its liquid at a given temperature. As temperature increases, more particles have enough energy to overcome intermolecular forces and transition into the vapor phase, thus increasing vapor pressure.
Raoult's law states that the partial pressure of each component in an ideal mixture is equal to the vapor pressure of the pure component multiplied by its mole fraction. This law is limited to ideal solutions where the vapor behaves like an ideal gas.
Behaviour of Vapor Pressure in Pure Component.
Raoult's Law (Blue Line) describes the vapor pressure of an ideal solution. According to Raoult's Law, the partial vapor pressure of component 1 (P1) is directly proportional to its mole fraction (X1) in the solution.
𝑃1 = 𝑋1𝑃1∗ ………..(2)
Where 𝑃1∗ the vapor pressure of pure component 1. The blue line shows a linear relationship starting from the origin and increasing proportionally with X1.
Non-Ideal Solution (Red Curve) represents the behavior of a real, non-ideal solution.
Deviates from the linear relationship predicted by Raoult's Law. The red curve shows either positive or negative deviation from the ideal behavior due to interactions between different molecules in the solution. Positive deviation (the curve is above the blue line) indicates weaker interactions between unlike molecules than like molecules. Negative deviation (the curve is below the blue line, not shown here) would indicate stronger interactions between unlike molecules.
Henry's Law (Dashed Line) applies at very low concentrations of component 1 (i.e., when X1 is close to 0). States that the vapor pressure of a solute is proportional to its mole fraction in the solution at low concentrations.
𝑃1 = 𝑘𝐻𝐻𝑋1 ………..(3)
Where 𝑘𝐻 is Henry's constant. The dashed line starts from the origin and has a steeper slope than Raoult's Law, indicating that at very low concentrations, the solute's vapor pressure increases more rapidly with mole fraction.
Positive Deviation.
The y-axis represents the vapor pressure of the solution. The x-axis represents the mole fraction of component A (Xa), which ranges from 0 to 1. The mole fraction of component B (Xb) is complementary, ranging from 1 to 0. The dashed lines represent the vapor pressures of the pure components 𝑝a (for A) and 𝑝b (for B) as functions of their mole fractions. These are linear because, according to Raoult's Law, the vapor pressure of a pure component in a solution is directly proportional to its mole fraction. The solid curve above the dashed lines represents the actual vapor pressure of the solution (𝑝= 𝑝a+ 𝑝b). This curve is higher than the dashed lines, indicating a positive deviation from Raoult's Law. Raoult’s Law (Positive Deviation) if the A-B interactions in solutions are weaker than the A-A and B-B interactions in the two liquids that make up the solution, then A and B kinds of molecules have a higher tendency to escape from the solution than from pure liquids.
Negative Deviation.
Negative deviation occurs when the intermolecular forces between unlike molecules (A- B) are stronger than those between like molecules (A-A or B-B). As a result, the vapor pressure of the solution is lower than predicted by Raoult's Law.