THERMODYNAMIC RELATIONS EQUILIBRIUM AND STABILITY
g is Gibbs function
When a gas is throttled then first its temperature increase (heating) as the pressure decrease but after a particular pressure, temperature decrease (cooling) as pressure decrease. At different initial temperature different such pressure exist.
- The curve connecting all transition point is inversion curve.
- The Joule-Thompson Coefficient is:
- For ideal gas μj = 0 i.e. in throttling process temperature of ideal gas remains constant.
- If initial temperature and pressure are within inversion curve, i.e. below maximum inversion temperature, cooling happens.
- Except Hydrogen and Helium the maximum inversion temperature of all the other gases is more than atmospheric temperature so cooling occurs in throttling of those gases.
- For Hydrogen and Helium maximum inversion temperature is below atmospheric temperature so heating occurs after throttling.
- For cooling of Hydrogen and Helium after throttling, they should initially be cooled below their maximum inversion temperature.
- There is no change in Temperature when an ideal gas is made to under go a Joule-Thompson expansion
- Clausis-Clayperon equation is a way of characterizing a discontinuous phase transition between two phases of matter of a single constituent.
- On a P-T diagram, the line separating two phases is known as the coexistence curve.
where dp/dT is the slope of the tangent to the co-existence curve at any point, l is the specific latent heat, T is the temperature and V is the specific volume change and S stands for specific entropy.
Sf = entropy of the final phase
Si = entropy of the initial phase
Vf = volume of the final phase
Vi = volume of the initial phase
Phase diagram for water and any other substance on p–T coordinates.
- Slope of sublimation curve at the triple point is greater than that of the vaporization curve.
i.e. (dy/dx)sublimation > (dy/dx)vaporization
- Gibbs phase rule for non reactive system
Degree of freedom:
f = c – p + 2
c — no. of components
p — no. of phases