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Showing posts with label THERMODYNAMICS:. Show all posts
Showing posts with label THERMODYNAMICS:. Show all posts

## Thursday, October 1, 2020

### How to distinguise between " Extensive and Intensive" thermodynamic properties?

Extensive and Intensive properties:

2: Ratio of two extensive property gives an intensive property.

3: An extensive property can be converted into intensive property by defining it per mole/        per gram/ per liter

Related Questions:

### What are properties of "thermodynamic system"?

The state of a system is defined by a particular set of its measurable parameters called properties, by which a system can be described for example, Temperature (T), Pressure (P) and volume (V) defines the thermodynamics state of the system.

Intensive property: After specifying the parameter of the system, when system is divided in parts the parameter whose value remains unchanged due to division is known as Intensive parameter or properties. the value of intensive  is independent of the  mass (size or quantity) of the system.
Refractive index
Surface tension
Viscosity
Molar Mass
Density
Free energy per mole
Specific heat capacity
Molar heat capacity
Free energy per mole
Pressure (P)
Temperature (T)
Boiling point
freezing point etc
Molar enthalpy
Molar conductivity
Equivalent conductivity
Molarity, Normality, Mole fraction,%w/w,%V/V
EMF of cell

Extensive property: the parameter  whose value change on division known as extensive properties and these are depends on the mass (size, quantity) of the system.
Volume
Number of moles
Mass
Mole
Free Energy (G)
Entropy (S)
Enthalpy (H)
Internal energy (E&U)
Heat capacity
K.E.
P.E.
Gibbs free energy (G)
Resistance
Conductance

Extensive and Intensive properties:

2: Ratio of two extensive property gives an intensive property.
3: An extensive property can be converted into intensive property by defining it per mole/        per gram/ per liter

### What are the path function in thermodynamics ?

Path function:

The thermodynamic Functions which depend on the path means how the process is carried out to reach a state from another  state depends on path e.g. work & heat.

State function: Pressure, volume, temperature, Gibbs's free energy, internal energy,     entropy
Path function: Work, Heat, Loss of energy due to friction

Note : S, U, H, V, T etc are state function but ∆S, ∆U, ∆H, ∆V, ∆T, etc.are not state function. Infact ∆ terms are not function itself and it is very misleading and frequently asked in the exams.

Related Questions:

### What are the Mathmatical conditions for state functions or state variables?

Mathematical Condition for a function to be a state function:-

There are three conditions that must be satisfied simultaneously for a function to be state      function.

(i) If ∆φ is a state function

It means change in depends only on end states and not on the path which it followed       during the process.

(ii) If ∆φ is a state function

It implies, in cyclic integral as the end states are same, so ∆φ value will be zero.

(iii) If ∆φ = f(x, y) is a state function, Euler's reciprocity theorem must be satisfied.

If dz=0 then, are we sure that z = 0 state function ?

"Change in state function (z) is fixed in between two states so ∆z is also
a state function example ∆P,∆T,∆V,∆H= state function is a wrong statement"

Related Questions:

### What are the "State functions or State variables" ?

State Functions or State Variables are the physical quantity having a definite value at a particular (present state) state and value is independent from the fact how the system achieved that state.

Mathematical Condition for a function to be a state function:-
There are three conditions that must be satisfied simultaneously for a function to be state      function.

(i) If ∆φ is a state function

It means change in depends only on end states and not on the path which it followed       during the process.

(ii) If ∆φ is a state function

It implies, in cyclic integral as the end states are same, so ∆φ value will be zero.

(iii) If ∆φ = f(x, y) is a state function, Euler's reciprocity theorem must be satisfied.

If dz=0 then, are we sure that z = 0 state function ?

"Change in state function (z) is fixed in between two states so ∆z is also
a state function example ∆P,∆T,∆V,∆H= state function is a wrong statement"

### Consider the chemical reaction at 300 K H2 (g) + Cl2 --> HCl(g) ΔH= -185KJ/mole calculate ΔU if 3 mole of H2 completely react with 3 mole of Cl2 (g) to form HCl.

H2 (g)+Cl2 -->  HCl(g) ΔH= -185KJ/mole
Δng=0
ΔH= ΔU+ ΔngRT
ΔH= ΔU
ΔHR= -185 KJ/mole ,ΔUR= -185 KJ/mole
H2 (g)+Cl2 --> HCl(g) ΔH= -185KJ/mole
3 mole       3 mole
Hence           ΔU= -185 X 3 KJ/Mole

### What is the relation between change in enthalpy (dH ) and change in internal (dE) for combustion of methan ?

For the given reaction:

CH4(g) + 2O2(g) ---------> CO2(g) + 2H2O(l)
dH = dE + dnRT
Dn = no. of mole of products - no. of moles of reactants = 1– 3 = –2
DH = DE – 2RT

### 1 mole of a real gas is subjected to a process from (2 bar, 40 lit.,300K) to (4 bar, 30 lit., 400 K). If change in internal energy is 35 kJ then calculate enthalpy change for the process.

DH = DU + D(PV)
D(PV) = P2V2 – P1V1
= 4 × 30 – 2 × 40
= 40 liter -bar = 4 kJ
so      DH = 35 + 4 = 24 kJ