Thermodynamics 3

Question 1

Enthalpy

Answer 1

Enthalpy change accompanying a process is defined as the sum of the increase in internal energy of the system and the pressure, volume, work done.

H = U + Pv

FOr a reaction, the change in enthalpy:

∆H = ∆U + p∆V

Question 2

Significance of ∆H from the first law of thermodynamics.

Answer 2

∆H is the heat evolved or absorbed in a reaction at constant temperature and pressure.

• For exothermic reaction, the chemical reaction which proceeds with the evolution of heat energy, ∆H is -ve.
• For endothermic reaction, the chemical reaction which proceeds with the absorption of heat energy, ∆H is +ve.

Question 3

Relationship between delta H and delta U

Answer 3

Delta H = delta U + Delta ng RT

Question 4

Extensive property

Answer 4

It is a property whose value depends on the quantity of size of matter present in the system.
Eg :- volume, internal energy, enthalpy, and heat capacity

Question 5

Intensive property

Answer 5

The properties which do it depend on the quantity or size of the matter present in the system.
Eg:- temperature, pressure, etc..

Question 6

Heat capacity

Answer 6

It is defined as the amount of heat acquired to raise the temperature of the system by 1 degree Celsius.
Eg:- C delta T
C=q/ deltaT

Question 7

Molar heat capacity

Answer 7

It is defined as the amount of heat required to raise 1mole of the substance by 1 degree Celsius
Cm = C/n

Question 8

Specific heat capacity

Answer 8

It is defined as the amount of heat required to raise the temperature of the 1 gum of a substance by 1 degree Celsius.
C=q/deltaT x m

Question 9

Relation between Cp and Cv

Answer 9

Cp- Cv = R