Calculate
Interpretation:
The standard entropy changesin thesurroundings of the given reaction and spontaneity of the given reactionis to be determined.
Concept introduction:
Entropy is the direct measurement of randomness or disorder. Entropy is an extensive property and it is a state function.
The enthalpy of the system is defined as the sum of the internal energy and the product of the pressure and volume. Enthalpy is a state of function and an extensive property.
Change in entropy of the system is the difference between the entropy of the final state and the entropy of the initial state.
The entropy of a system and the entropy of the surroundings comprise the entropy of the universe.
Enthalpy change of a reaction is the difference between the enthalpies of the reactants and the products.
For a spontaneous reaction,
Answer to Problem 20QP
Solution:
a)
The reaction is spontaneous.
b)
The reaction is not spontaneous.
c)
The reaction is spontaneous.
Explanation of Solution
a)
The entropy change of the universe, for this reaction, is calculated using the following expression:
Here,
The enthalpy change of the system
The standard enthalpy change of the reaction
Here,
The enthalpy of reaction is as follows:
From appendix
Substitute the standard enthalpy change of the formationvalues of the substancesin the above expression,
Substitute the values of
Therefore, the entropy change of the system is
Calculate the entropy change for the system.
The entropy change for the system is calculated using the following expression:
Here,
Calculate the standard entropy change of the given reaction.
The standard entropy change for this reaction is calculated using the following expression:
From appendix 2, the standard entropy value of the substance is as follows:
Substitute the standard entropy values of the substance in the above expression,
The entropy change of the universe is calculated using the following expression:
Substitute the values of
Therefore, entropy change of the universe for this reaction is
For a spontaneous of reaction, the value of
The entropy change of the universe for this reaction is positive.
Therefore, the reaction is spontaneous.
b)
The entropy change of the universe for this reaction is calculated using the followingexpression:
Here,
The enthalpy change of the system
The standard enthalpy change of the reaction
Here,
The enthalpy change for the reaction is as follows:
From appendix 2, the standard enthalpy change of the formation of the substance is as follows:
Substitute the standard enthalpy change of the formation value of the substance in the above expression,
The standard entropy change for this reaction is calculated using the followingexpression:
Substitute the value of
Therefore, the entropy change of the system is
Calculate the entropy change for the system.
The entropy change for the system is calculated using the following expression:
Here,
Calculate the standard entropy change of the given reaction.
The standard entropy change for this reaction is calculated using the followingexpression:
Here,
From appendix 2, the standard entropy value of the substance is as follows:
Substitute the standard entropy value of the substance in the above expression,
Therefore, the standard entropy change for this reaction is
Calculate the entropy change of the universe.
The entropy change of the universe is calculate using the following expression:
Substitute the value of
Therefore, entropy change of the universe for this reaction is
For a spontaneous reaction, the value of
The entropy change of the universe for this reaction is negative.
Therefore, the reaction is not spontaneous.
c)
Calculate entropy change of the universe for the given reaction.
The entropy change of the universe for this reaction is calculated using the following expression:
Here,
The enthalpy change of the system
The standard enthalpy change of the reaction,
Here,
From appendix 2, the standard enthalpy change of the formation of the substance is as follows:
Substitute the standard enthalpy change of the formation value of the substance in the above expression,
The standard entropy change for this reaction is calculated using the followingexpression:
Substitute the values of
Therefore, the entropy change of the system is
Calculate the standard entropy change of the given reaction.
The standard entropy change for this reaction is calculated using the following expression:
Here,
From appendix 2, the standard entropy value of the substance is as follows:
Substitute the values of standard entropy value of the substances in the above expression,
Therefore, the standard entropy change for this reaction is
Calculate the entropy change of the universe.
The entropy change of the universe is calculated using the following expression:
Substitute the values of
Therefore, entropy change of the universe for this reaction is
For a spontaneous reaction, the value of
The entropy change of the universe for this reaction is positive.
Therefore, the reaction is spontaneous.
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Chapter 18 Solutions
Chemistry
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