Thermodynamics

Question 1

What is thermodynamics?

Answer 1

It is the study of change in temperature of a body

Question 2

Define the following terms
1. System
2.Surrounding
3.Universe

Answer 2

1. System can be defined as the body who’s temperature change is been studied
2. Surrounding: everything that surrounds the system
   3.Universe: the system and the surrounding together

Question 3

What are the different types of system?

Answer 3

The different types of system are:
1. Closed system: no transfer of matter
2. Open system: energy and matter both are transferred
3. Isolated system: no transfer of energy and matter both

Question 4

What are the different types of process?

Answer 4

1. Isochoric: the volume stays constant
2. Isobaric: the pressure stays constant
   3.Isothermal: the temperature stays constant
   4.Adiabatic: an isolated system process

Question 5

What is path function and state function?

Answer 5

Path function are those variable that depend on the was that state is attained like work, heat
While state function depends on the initial and final state of the system like V, P,TT enthalpy

Question 6

Classify Heat capacity and specific heat capacity on the bases of intensive and extensive properties ?

Answer 6

SI unit of C(heat capacity) = J/k
SI unit of c(specific heat capacity) = J/K kg
thus heat capacity is intensive and specific heat capacity is extensive

Question 7

What is the formula to calculate the work done in a reversible process ?

Answer 7

-2.303Rt log(pi/pf)
or
-2.303Rt log(Vf/Vi)

Question 7

What are intensive and extensive properties?

Answer 7

Intensive properties are those that are independent of mass like density, temperature, pressure and
while extensive are those that depend on the mass of the substance like volume, enthalpy ,gibis free energy

Question 8

Work =

Answer 8

F.d = -PΔV

Question 9

What is the first law of thermodynamics ?

Answer 9

The first law is
ΔU = Q + W
= Q -PΔV

Question 10

2nd law

Answer 10

Exothermic reaction is spontaneous due to the release of energy during the process that increases the temperature
ΔS>= 0

Question 11

3rd law

Answer 11

When the temperature hits 0 k or -273.15 C then the spontaneity of aa solid crystalline is zero

Question 12

What are the sign conventions for the following:
1. work done on the system
2. Work done by the system
3. Endothermic reaction
4. Exothermic reaction

Answer 12

1. • ve
2. • ve
3. • ve
4. • ve

Question 13

Enthalpy

Answer 13

A state function that measures the the total change in the energy levels of a system.
ΔH =ΔU +PΔV

Question 14

ΔU means

Answer 14

internal energy or the sum of all the Ke and PE of the system
it depends only on temperature

Question 15

ΔH =
(for gases)

Answer 15

pΔV = ΔngRT
ΔH = ΔU +ΔngRT
Δng = products - reactants (moles)

Question 16

What is Standard enthalpy? And what are their types?

Answer 16

Standard enthalpy is the enthalpy measured at 1 atm pressure and 298 K . There are two types:
1. Standard enthalpy of formation(ΔfH): it concentrates on the number of moles formed.
ΔfH = ΔrH/ no of moles in the product

2. Standard enthalpy of reaction(ΔrH): this mainly focuses on the enthalpy change

Question 17

What are different type of enthalpy? (on the bases of state change)

Answer 17

1. Enthalpy of fusion (ΔfusH ): amount of energy required to convert 1 mole of solid into liquid.
   Δ H = +ve
2. Enthalpy of vaporization (ΔvapH): the energy required to convert 1 mole of liquid into vapours at boiling point
   Δ H = +ve
3. Enthalpy of sublimation(ΔsubH): the energy required to change 1 mole of solid directly into gas
   Δ H = +ve

Question 18

Hess’s law

Answer 18

that the change of enthalpy in a chemical reaction is the same regardless of whether the reaction takes place in one step or several steps, provided the initial and final states of the reactants and products are the same.
Δ T = 0

Δ Ht = Δ H1 + Δ H2…….

Question 19

What are the different types of standard enthalpy (on the bases of reaction)?

Answer 19

1. Combustion (ΔcH∘): energy required to burn 1 mole of a substance
2. Atomization(ΔaH∘): energy required to break one mole f a compound into atoms
3. Lattice(ΔlatticeH∘): energy required to break 1 mol of ionic compound into ions in gaseous state
4. Solution(ΔsH∘): energy required to add 1 mol of solute in a specific solvent
5. Dilution(ΔdH∘): the change in the value of ΔH when solvent is added

Question 20

What is thermal equation?

Answer 20

it a balanced equation with the value of ΔH given

Question 21

Bond harbor’s cycle

Answer 21

It is a method used to calculate the standard lattice enthalpy change of a reaction by using other types of enthalpy change leading to ionization

Question 22

Entropy

Answer 22

the measure of disorderness or randomness in a substance
Factors
1. heat
2. temperature
ΔS = 0 reversible reactions
ΔS > 0 for irreversible reactions

Question 23

Spontaneity

Answer 23

Self occurring reaction. A reaction that doesn’t need external interference to happen.
Factors:
1. entropy
2. enthalpy

Question 24

Gibbs free energy

Answer 24

A state function that tells about the spontaneity of a reaction

ΔG = ΔH - TΔS

ΔG>0, ΔH > TΔS not spontaneous
ΔG<0, ΔH < TΔS spontaneous