**Answer key: γ= 1.54**

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**THERMODYNAMICS:**. Show all posts## Friday, September 29, 2023

## Thursday, October 1, 2020

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

**Extensive and Intensive properties:**

1:
Extensive properties are additive but intensive properties are non additive.

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 the "State functions or State variables" ?

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

### What are the path function in thermodynamics ?

### What are the path function in thermodynamics ?

### 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:**

1:
Extensive properties are additive but intensive properties are non additive.

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

### What are the path function in thermodynamics ?

** Path function:**

**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. In*

*fact ∆ terms are not function itself and it is very misleading and frequently asked in the exams.*

### 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.

**H**

_{2 }(g)+Cl

_{2}

_{--> }

_{}HCl(g) ΔH= -185KJ/mole

**Δng=0**

**ΔH= ΔU+ ΔngRT**

ΔH= ΔU

ΔH

_{R}= -185 KJ/mole ,ΔU_{R}= -185 KJ/mole
H

_{2 }(g)+Cl_{2}_{--> }_{}HCl(g) ΔH= -185KJ/mole**3 mole 3 mole**

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

**For the given reaction:**

CH

_{4}(g) + 2O_{2}(g) ---------> CO_{2}(g) + 2H_{2}O(l)

*dH = dE + d***nRT**

Dn = no. of mole of products - no. of moles of reactants = 1– 3 = –2

**DH = D**

**E – 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) = P

_{2}V_{2}– P_{1}V_{1}_{ }= 4 × 30 – 2 × 40

= 40 liter -bar = 4 kJ

so DH = 35 + 4 = 24 kJ

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