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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:

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.
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.
 

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"

The heats of solution of anhydrous CuSO4 and hydrated CuSO4.5H2O are 66.5 and 11.7 kJ mol1 respectively. Calculate the heat of hydration of CuSO4 to CuSO4.5H2O.

 


200 ml of KOH and 200 ml of HNO3 of same molarity are mixed together and liberated 3.426 kJ of heat. Determine the molarity of each solution.

 



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

Calculate the work performed when 2 moles of hydrogen expand isothermally and reversibly at 25”C from 15 to 50 litres.

 


A gas absorbs 200J of heat and expands against the external pressure of 1.5 atm from a volume of 0.5 litre to 1.0 litre, Calculate the change in internal energy.

 


The internal energy of one mole of a gas is

 


A system does 100J work on surroundings by absorbing 150J of heat. Calculate the change in internal energy

 


Calculate the heat of neutralization by mixing 200ml of 0.1M H2SO4 and 200 ml of 0.2 M KOH if heat generated by the mixing is 2.3 KJ

 


The specific heats of iodine vapours and solid are 0.031 and 0.055 Cal/g respectively. If heat of sublimation of iodine is 24Cal/g at 200”C, What is its value at 250”C.

 


How much heat is produced when 4.50g methane gas is burnt in a constant pressure system.

 


Two mol of an ideal gas is expanded isothermally and reversibly at 300 K to twice the original volume. Calculate q, w, E, and H.

 


1.5 mol of a perfect gas at 300 K is compressed reversibly and isothermally from a pressure of 1.01x10^5 N m^2 to 5.05x106 Nm^2. Calculate the amount of work done.