CHE 320: Chapter 6 Summary

Phase Diagrams

  • Key Points:
    • Phase diagrams display equilibrium states of matter under varying conditions.
    • Important points:
    • Point A: 20°C, 3 mm Hg (Vapor)
    • Point B: 20°C, 17.54 mm Hg (Liquid)
    • Point C: 20°C, 760 mm Hg (Liquid)
    • Point D: 100°C, 760 mm Hg (Vapor)
    • Point E: 130°C, 760 mm Hg (Vapor)

Vapor Pressure

  • Equations:
    • Vapor pressure on the VLE curve: P=P∗P = P^*
    • Relation: dP∗/dT=ΔH<em>VT(V</em>g−Vl)dP^*/dT = \frac{\Delta H<em>V}{T(V</em>g - V_l)}
    • Where:
      • ΔHV\Delta H_V: Specific latent heat of vaporization
      • VgV_g: Specific molar volume of gas
      • VlV_l: Specific molar volume of liquid

Clausius-Clapeyron Equation

  • Derives the relationship between pressure and temperature for phase changes.
    • ln⁡P∗=−ΔHVRT+B\ln P^* = - \frac{\Delta H_V}{R T} + B
    • Used to calculate vapor pressures at different temperatures.

Gibbs Phase Rule

  • Degree of freedom calculated as: DoF=2+c−Π−rD_o F = 2 + c - \Pi - r
    • Where:
    • cc: number of components
    • Π\Pi: number of phases
    • rr: number of independent reactions

Dew Point & Bubble Point

  • Dew Point: Temperature at which the first drop of liquid is formed at constant pressure.
  • Bubble Point: Temperature at which the first bubble of vapor is formed at constant pressure.

Antoine Equation Constants

  • Used for calculating vapor pressures:
    log⁡10P=A−BT+C\log_{10} P = A - \frac{B}{T + C}
  • Constants differ by substance.

Relative Saturation

  • Relative humidity defined as:
    S<em>r=p</em>ipi∗×100%S<em>r = \frac{p</em>i}{p_i^*} \times 100\%

Note on Calculations

  • Always check ranges for validity in calculations, especially with Antoine constants and phase behaviors.