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SIR CAN U PLZ PUT NOTES OF THERMODYNAMICS.

1. What is system ?

System is the part of the universe under observations are made and remaining universe constitutes the surroundings .The surroundings include everything other than the system. System and the surroundings together constitute the universe .The remaining part is called the surroundings .System and the surroundings together constitute the universe .

That is universe   = system + surroundings

The wall separate the system from the surroundings is called the boundary .

2. What are different types of system ?

        Types of system

        1.  Open system     :  Exchanges both matter and energy with the surroundings. The presence of reactants in an open beaker is an example of an open system .

         2. Closed system     :  Exchanges energy but not matter with the surroundings.The presence of reactants in a closed vessel made of conducting material is an example of a closed system .

         3.Isolated system   :  Exchanges neither energy nor matter with the surroundings .The presence of reactants in a thermoflask or any other closed insulated vessel is an example of an isolated   system .example :- cup of coffee.

3. Derive the equation for work done by a reversible process:

4. Write Gibb's Helmholtz equation and explain.

Gibb's free energy is an extensive property denoted by G is defined as the energy which is available to do useful work.

G = H - TS

? G = ?H - T ? S - S ? T

At constant temperature ? T = 0

? G = ? H - T ? S. This is known as Gibb's Helmholtz equation.

5. Calculate the number of kJ of heat necessary to raise the temperature of 60.0 g of aluminium from 35^oC. Molar heat capacity of Al is 24J mol^-1 K^-1.

m = 60g

t₁ = 35^oC

? T = 55-35  = 20

M = 27

T₂ = 55^o   

Cm = 24J/ mol K

q = n Cm ? T= m/M ×Cm × ?T

= 60/27 × 24 × 20J = 1067J = 1.067 kJ

6. Enthalpy of combustion of carbon to CO₂ is - 393.5 kJ mol^-1. Calculate the heat released upon formation of 35.2 g of CO₂ from carbon and dioxygen gas.

7. Enthalpies of formation of CO(g). CO₂(g). CO₂(g), N₂O(g) and N₂O₄(g) are -110, -393, 81 and 9.7 kJ mol^-1 respectively. ? H for the reaction:

N₂O₄(g) + 3CO(g)    ? N₂ O (g)  +  3CO₂(g)

C + ½O₂ ? CO         ^-110kJ

C + O₂  ? CO₂        ^-393 kJ

N₂ + ½ O₂ ? N₂O     81 kJ

N₂ + 2O₂ ? N₂O₄     9.7 kJ

N₂O₄ + 3CO ? N₂O + 3CO₂ 

9.7    3 × -110   81      3 × -393

? H = [81 + 3× (^-393)] - [9.7 + (3 × ^-110)]

= ^-1098 - (^-320.3)

= ^-777.7 KJ

8. Given

N₂ (g) + 3H₂(g) ? 2NH₃;

?_rH^? = ^-92.4kJ mol^-1

What is the standard enthalpy of formation of NH₃ gas?

N₂ (g) + 3H₂(g) ? 2NH_{3 (g)}

?_rH^? = ^-92.4kJ mol^-1 

N₂(g) + 3H₂(g) ? 2NH₃;

?_rH^? = ^-92.4kJ mol^-1

9. Calculate the standard enthalpy of formation of CH₃OH(l) from the following data:

CH₃OH(l) + 3/2 O₂ (g) ? CO₂ (g) + 2H₂O (l); ?_r H^?

= -726 kJ mol^-1

C(graphite) + O₂ (g) ? CO₂ (g); ?_c H = ^-393 kJ mol^-1

H₂(g) + ½ O₂(g) ? H₂O(l) ?_fH^? = ^-286 kJ mol^-1

C + O₂ ? CO₂            ^-393 kJ 

2H₂ + O₂ ? 2H₂O

2 × ^-286 = ^-572kJ

CO₂ + 2H₂O ? CH₃OH + 3/2 O₂ = ⁺726 kJ

C + 2H₂ + ½O₂ ? CH₃OH  -239 kJ/mol

10. Calculate the enthalpy change for the process

CCl₄(g) ? C(g) + 4 Cl (g) and calculate bond enthalpy of C - Cl in CCl₄(g).

?_vap H^? (CCl₄) = 30.5 kJ mol^-1

?_fH^? (CCl₄) = -135.5 kJ mol^-1

? _a H^? (C) = 715.0 kJ mol^-1, where ?_a H^? is enthalpy of atomisation.

? _a H^? (Cl₂) = 242 KJ mol^-1

CCl₄(l) ? CCl₄(g) ? H_{vap = 30.5 kJ}

? H_vap =? H _CCl4 (g) - ? H_CCl4 (l)

30.5 = ? H_CCl4 (g) - (-135.5)

? H_CCl4 (g) = -135.5 + 30.5 = -105 kJ/mol

CCl₄(g) ? C (g) + 4Cl(g)

? H = ? H_c(g) + ? H_Cl (g) - ? H_CCl4 (g)

11. For the reaction,

2A(g) + B (g) ? 2D(g)

? U^? = -10.5 kJ and ? S^? = -44.1 JK^-1. Calculate ? G^? for the reaction, and predict whether the reaction may occur spontaneously.

2A (g) + B (g) ? 2D(g)

? n = 2-(2 + 1) = -1

? H = ? u + ? nrt

The reaction is non spontaneous as ? G is positive.

12. The equilibrium constant for a reaction is 10. What will be the value of ? G^?? R = 8.314 JK^-1, T = 300K.

 ? G^? = -2.303 RT log K. 

= -2.303 × 8.314 × 300 × log 10

= -5744.1 J

13. Comment on the thermodynamic stability of NO(g), given

½ N₂ (g) + ½ O₂(g) ? NO (g);

 ? _r H^? = 30 kJ mol^-1

NO(g) + ½ O₂(g) ? NO₂(g)

:  ?_r H^? = - 74 kJ mol^-1 

NO is thermodynamically not stable as its formation is endothermic.

14. Derive an equation for enthalpy of a system:

The heat content of a system is called enthalpy. It is denoted by H.

Internal energy change, ? U = q_p - P ? V 

ie, U₂ - U₁ = q_p - P (V₂ - V₁)

q_p              = (U₂ - U₁) + P (V₂ - V₁)

                  = (U₂ + PV₂) - (U₁ + pv₁)

U + PV      = H the enthalpy of the system.

q_p = H₂ - H₁ or ? H = ?U + P ? V = ? H 

? H = -ve

Exothermic process (heat energy is liberated),

? H = +ve.

Endothermic process (heat energy is absorbed)

At constant volume ? H = ? U

In the cases of gaseous changes

PV₁ = n₁ RT

PV₂ = n₂RT

P (V₂ - V₁) = n₂ RT - n₁ RT

P ? V         = (n₂ - n₁) RT

P ? V         = ? n RT

? H            = ? u + ? n RT