Name: Absolute Zero and Third Law of Thermodynamics
Uploaded: 2019-07-19
Duration: 20 min
Description: In this video, you will learn what absolute zero and the third law of thermodynamics is. You will also learn about the significance of the third law of therm...

Question

What do symbols

ΔH, ΔS

and

ΔG

signify? How are they inter-related? What is the importance of the relation formed?

Accepted Answer

1. $∆ H$ : It is enthalpy of the system which is represented by $H$ and $∆ H$ means change in the initial and final values of enthalpy. This is an extensive property.

$∆ H = H_{2} - H_{1} .$

Where,

$H_{2} =$ final value and

$H_{1} =$ initial value

2. $∆ S$ is the entropy change of the substance. Its value also depends on initial and final one.

$∆ S = S_{2} - S_{1} .$

$S_{2} =$ final value and

$S_{1} =$ initial value.

3. $∆ G =$ Free energy or Gibbs' free energy: It is the total non-expansion of work that a system can do or measure of amount of energy available to do work in an isothermal and isobaric process.

The inter-relation among enthalpy, entropy and free energy change is given by,

$∆ G = ∆ H - T ∆ S .$

Importance: In the relation, value of $∆ G$ can be predicted for the reaction.

For favourable reaction, $∆ G > 0$ .

For non-favourable, $∆ G < 0$ .

For Cyclic process, $∆ G = 0$ .

What do symbols $ΔH, ΔS$ and $ΔG$ signify? How are they inter-related? What is the importance of the relation formed?

Important Questions on Thermodynamics

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