   Chapter 18, Problem 88SCQ

Chapter
Section
Textbook Problem

Under what conditions is the entropy of a pure substance 0 J/K · mol? Could a substance at standard conditions at 25 °C have a value of 0 J/K · mol? A negative entropy value? Are there any conditions under which a substance will have negative entropy? Explain your answer.

Interpretation Introduction

Interpretation:

It should be explained that under what conditions the pure substances entropy will be zero, the negative entropy value, the substance at 25oC have zero entropy and conditions at which the substance will have negative entropy.

Concept introduction:

Entropy is a measure of the randomness of the system. It is a thermodynamic quantity and an extensive property. It is represented by the symbol S. It can also be defined as the degree of energy dispersal. More the dispersal in energy, more is the value if entropy.

The standard entropy change for any reaction is the sum of standard molar entropies of product, subtracted from the sum of standard molar entropies of reactants. The standard molar entropies are multiplied by the stoichiometric coefficient which is as per the balanced equation.

ΔrS°nS°(products)nS°(reactants)

Explanation

According to third law of thermodynamics, the entropy of a substance is zero at absolute zero temperature. Thus, The entropy of a pure substance is 0 J/Kmol when the temperature is zero.

A substance cannot have 0 J/Kmol entropy at standard conditions at 25 °C. This is because there are some motions that are always involved with the substance which can be either rotational or vibrational due to which entropy is never zero at 25 °C

Still sussing out bartleby?

Check out a sample textbook solution.

See a sample solution

The Solution to Your Study Problems

Bartleby provides explanations to thousands of textbook problems written by our experts, many with advanced degrees!

Get Started 