Thermodynamics

Question 1

State and Explain three types of system.

Answer 1

Open system:- Both exchange of mass and heat tales place
Closed system :- No exchange of mass, only heat exchange
Isolated system :- No heat or mass exchange

Question 2

What is universe?

Answer 2

Surrounding + System is universe.

Question 3

What are intensive properties of thermodynamics?

Answer 3

Properties which doesn’t depends upon the quantity or size of matter present.
Eg:- surface tension and temperature

Question 4

What are extensive properties of thermodynamics?

Answer 4

Properties which depends upon physical body features like quantity and size.
Eg :- heat capacity and enthalpy

Question 5

What are two types of functions?

Answer 5

State function and Path Function.

Question 6

What is state function?

Answer 6

The property which depends on the state of a system and independent of a path followed to attain it, is called state function.
Eg :- Pressure and Volume

Question 7

What is path function?

Answer 7

Property which depends upon the path is called path function.
Eg:- heat(Q) and work(W)

Question 8

What are different types of thermodynamic processes?

Answer 8

1) Isothermal process
2) Isobaric Process
3) Isochoric Process
4) Adiabatic process

Question 9

Explain Isothermal process.

Answer 9

Isothermal process has
Constant = T(temperature)
No change in temperature

Question 10

Explain Isobaric Process

Answer 10

Isobaric Process has
Constant = P (pressure)
Change in pressure= 0

Question 11

Explain Isochoric Process.

Answer 11

Isochoric Process has
Constant = Volume (V)
Change in v = 0

Question 12

Explain Adiabatic Process.

Answer 12

In adiabatic process
There is no exchange of heat between system and surrounded
Q(heat) = zero

Question 13

Importance of zeroth law of equilibrium

Answer 13

Zeroth law established temperature as indicator of thermal equilibrium

Question 14

State first law of thermodynamics

Answer 14

First Law of Thermodynamics
Energy can neither be created nor destroyed although it can be
converted from one form to the other.
Mathematically, ∆ = + U q W
where, ∆ = U internal energy change
q = heat added to system
W = work added to system

Question 15

State the sign convention for first law of thermodynamics

Answer 15

Sign convention
(i) q is + ve = heat is supplied to the system
(ii) q is – ve = heat is lost by the system
(iii) W is +ve = work done on the system
(iv) W is –ve = work done by the system

Question 16

What is irreversible process

Answer 16

The process which cannot be reversed
and amount of energy increases. All natural processes are
irreversible.

Question 17

What is internal energy

Answer 17

It is the total energy within the substance. It is the sum of many types
of energies like vibrational energy, translational energy, etc. It is an
extensive property and state function.
Its absolute value cannot be determined but experimentally change in
internal energy ( ) ∆U can be determined by
∆ = − U U U 2 1 or Σ − Σ U U P R
For exothermic process, ∆ = − U ve, whereas for endothermic process
∆ = U +ve.
U depends on temperature, pressure, volume and quantity of matter
and is independent of the method by which state has been attained.

Question 18

State the zeroth law of thermodynamics

Answer 18

The law states that if the two systems are in thermal equilibrium with
a third system then they are also in thermal equilibrium with each
other. Temperature is used here to know whether the system is in
thermal equilibrium or not.

Question 19

State Hess’s law

Answer 19

Overall the enthalpy change for a reaction is equal to sum of enthalpy change of individual steps in the reaction

Question 20

What is spontaneous process

Answer 20

The process which has a natural tendency to occur and do not require any external influence for their occurance are spontaneous process

Question 21

Features of spontaneous process

Answer 21

1) it occurs on its own and does not require any external agency to occur.
2) it proceeds in one direction and cannot take place in the opposite direction unless the external stimulant is present.
3) the spontaneous processes can be rapid or slow or spontaneity is not concerned with rate of the reaction
4) the spontaneous process continues till equilibrium reached. It is a natural process that tend to move in direction that leads to equilibrium.

Question 22

What is entropy? Give it’s unit

Answer 22

Entropy is a measure of molecular disorder or randomness.
The entropy change of a system is equal to the amount of heat transferred to it in a reversible manner divided by the temperature in kelvin at which the transfer takes place. Thus,
∆S = Qrev/ T