Thermochemical

Question 1

Definition Of Thermodynamics

Answer 1

The branch of science deals with the different forms of energy, the quantitative relation between them, and energy changes taking place during the physical and chemical properties.

Question 2

Define System, Surrounding, Boundary & Universe

Answer 2

System: Part of the universe under thermodynamic study eg- Chemical reaction taking place in a beaker
Surrounding
: Remaining portion of the universe other than the system
eg- everything outside the beaker containing chemical reaction
Boundary: The part or a surface that separates the system and its surroundings eg- glass beaker
Universe: The sum of system and surroundings.

Question 3

What are the types of Systems?

Answer 3

Open system: Exchange of matter and energy takes place
Closed system: Exchange of energy takes place not matter
Isolated system: Nothing gets exchanged

Question 4

Extensive and Intensive Definition

Answer 4

Extensive: Any property of a system whose magnitude is dependent on the quantity of matter present in the system
Intensive: Any property of a system that does not depend on the quantity of matter present in the system

Question 5

Define state variables & state of a system

Answer 5

State variables are the measurable thermodynamic property that determines the state of a system
State of the system are the specifying values of state variables

Question 6

Define state and path function

Answer 6

State function: The property of a system that depends on the current state and is independent of the path followed
Path function: The property of a system that depends on the path followed to reach the state.

Question 7

What are thermodynamic processes

Answer 7

1. Isothermal: Temperature constant hence internal energy constant
2. Adiabatic: Heat neither enters nor leaves the system
3. Isochoric: Volume is constant hence work done is also constant
4. Isobaric: Pressure is constant
5. Cyclic: The process in which a series of changes takes place and returns to the initial state
6. Reversible: Any process conducted in such a manner that the driving force is infinitesimally greater than the opposing force by a slight increase in the opposing force process can be reversed
7. Irreversible: The uni-directional process which proceeds in a definite direction and cannot be reversed at any stage

Question 8

Define Internal Energy

Answer 8

Every substance is associated with a definite form of energy that depends upon its chemical nature and state of existence

Question 9

First Law of Thermodynamics

Answer 9

According to Einstein’s equation first law of thermodynamics states that the total mass and internal energy of an isolated system remains constant

Question 10

Sign Conventions of heat, WD, IE

Answer 10

Heat: absorbed = +ve
released/ evolved = -ve
WD: WD on the system by the surrounding = +ve
WD by the system on the surrounding = -ve
IE: increase = +ve
decrease = -ve

Question 11

Define Enthalpy

Answer 11

It is defined as the sum of internal energy and energy that arises due to pressure-volume

Question 12

Define heat capacity, specific heat capacity, molar heat capacity, molar heat capacity at constant volume CV, and molar heat capacity at constant pressure

Answer 12

1. Heat Capacity: the amount of heat needed to raise the temperature by 1C or 1K
2. Specific Heat Capacity: the amount of heat needed to raise the temp of 1gm of substance by 1C or 1K
3. Molar Heat Capacity: the amount of heat needed to raise the temperature of 1 mole of gas by 1C or 1K
4. Molar Heat Capacity at constant volume CV: the amount of heat needed to raise the temperature of 1 mole of gas by constant volume
5. Molar Heat Capacity of constant pressure: the amount of heat needed to raise the temperature of 1 mole of gas by constant pressure

Question 13

Define Hess’s Law

Answer 13

Hess’s law states that the enthalpy change of a reaction remains same wether the reaction takes place in one step or series of steps

Question 14

Spontaneous & Non-spontaneous Process

Answer 14

1. Spontaneous Process: The process which takes place on its own without external influence
2. Non-spontaneous Process: The process which does not take place on its own without external influence but can be done by a continuous external supply of energy reverse of all spontaneous are non-spontaneous process

Question 15

Second Law of Thermodynamic

Answer 15

1. The second law of thermodynamics state that the spontaneous flow of heat is always unidirectional
2. Heat cannot be completely converted into work done unless there are permanent changes in the system or surrounding
3. No machine has yet been discovered which has an efficiency of unity

Question 16

Define Entropy and change in Entropy

Answer 16

Entropy: It is measure of disorderness or randomness of molecule
Change in Entropy: it is defined as heat absorbed in a reversible manner divided by the temperature at which change takes place

Question 17

Gibb’s Free Energy and change in Gibbs free energy

Answer 17

The energy available in system for doing useful work is called as Gibb’s Free Energy
Change in Gibbs free energy is defined as the difference between change in enthalpy and product of temperature nd Entropy change.

Question 18

Second Law of thermodynamics

Answer 18

It states that, “The total entropy of the universe (i.e., system and surrounding) increases in a spontaneous process

Question 19

Bond enthalpy

Answer 19

The amount of energy required to break one mole of gaseous molecule into a gaseous atom

Question 20

3rd law of thermodynamics

Answer 20

It states that total entropy of a perfectly ordered crystalline substance is zero at absolute zero temperature T=0 & S=0

Question 21

0th law of thermodynamics

Answer 21

It states that if ‘A’ & ‘B’ are in thermal equilibrium with each other and A and C are also in thermal equilibrium equilibrium with each other then it means B and C are also in thermal equilibrium with each other