what can be said about an endothermic reactio
What can be said about an Endothermic reaction with a negative entropy change?
The reaction is
1. spontaneous at all temperatures.
2. spontaneous at high temperatures.
3. spontaneous at low temperatures.
4. spontaneous in the reverse direction at all temperatures.
5. nonspontaneous in either direction at all temperatures.
What can be said about an Exothermic reaction with a negative entropy change?
The reaction is
1. spontaneous at all temperatures.
2. spontaneous at high temperatures.
3. spontaneous at low temperatures.
4. spontaneous in the reverse direction at all temperatures.
5. nonspontaneous in either direction at all temperatures.
Concepts and reason
The concepts used to solve this question are the characteristics of endothermic and exothermic reactions, and the Gibbs free energy equation to determine a spontaneous reaction.
what can be said about an endothermic reactio
Fundamentals
The change in Gibb’s free energy at constant temperature and pressure is given as;
Part 1
The question states that it is an endothermic reaction with negative entropy. This means that the change in enthalpy will be positive and change in entropy will be negative. That is
An endothermic reaction generally requires energy from the surroundings for it to proceed. The energy absorbed is usually in the form of heat. Therefore, the change in enthalpy of an endothermic reaction will always be positive. A negative change in entropy indicates that there is a decrease in disorder, with respect to the reaction.
The change in Gibb’s free energy at constant temperature and pressure is given as-
Now, the change in enthalpy and change in entropy can be written as follows,
Substitute these values in the above equation;
,thus, the reaction is spontaneous in the reverse direction at all temperatures.
Part 1
The reaction is spontaneous in the reverse direction at all temperatures.
One can make a mistake while substituting the signs in the Gibb’s equation. This in turn results in a miscalculation of the final answer. This can be avoided by keeping in mind the given conditions of the reaction and very attentively substituting the signs of the values.
Part 2
The question states that it is an exothermic reaction with negative entropy. This means that both the change in enthalpy and change in entropy will be negative. That is;
An exothermic reaction generally releases energy to the surroundings. The energy is usually released in the form of heat. Therefore, the change in enthalpy H of an exothermic reaction will always be negative. A negative change in entropy S indicates that there is a decrease in disorder, with respect to the reaction.
The change in Gibb’s free energy at constant temperature and pressure is given as-
Now, the change in enthalpy and change in entropy can be written as follows,
Substitute these values in the above equation;
Part 2
The reaction is spontaneous at low temperatures.
According to the sign convention in this equation,
This can occur only at low temperatures (T has small values). Thus, this reaction is spontaneous at low temperatures.
Part 1
The reaction is spontaneous in the reverse direction at all temperatures.
Part 2
The reaction is spontaneous at low temperatures.
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Answer:
spontaneous in the reverse direction at all temperatures.
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We’re being asked to identify which statement is correct for a reaction given the sign of its ΔH and ΔS.
The statements given describe the spontaneity of the reaction at different temperatures.
Recall that we can determine the spontaneity of the reaction based on the signs of ΔH and ΔS.
We can use the Punnett square shown below:
• +ΔH and +ΔS → spontaneous only at high temperatures• +ΔH and –ΔS → nonspontaneous at all temperatures• –ΔH and +ΔS → spontaneous at all temperatures• –ΔH and –ΔS → spontaneous only at low temperatures
Given:
Negative entropy change: –ΔS → negative value
We don’t know the sign of ΔH. ΔH → ??
Recall that:
• Exothermic reactions: lose energy and involve bonds breaking; ΔH is negative
• Endothermic reactions: gain energy and involve bonds forming; ΔH is positive
Since the reaction is endothermic → +ΔH → positive value
+ΔH and –ΔS
• +ΔH and –ΔS → the reaction is nonspontaneous at all temperatures
Therefore, the only true statement about the reaction is e.) nonspontaneous in either direction at all temperatures.
What can be said about an Endothermic reaction with a negative entropy change?The reaction isa. spontaneous at all temperatures.b. spontaneous at high temperatures.c. spontaneous at low temperatures.d. spontaneous in the reverse direction at all temperatures.e. nonspontaneous in either direction at all temperatures.
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what can be said about an endothermic reactio
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what can be said about an endothermic reactio
If you forgot your password, you can reset it.
In this problem, we are asked to determine the spontaneity of the endothermic reaction with negative entropy.
The statements given describe the spontaneity of the reaction at different temperatures.
Recall that when ΔH and ΔS are given, we can determine the spontaneity of the reaction based on their signs.
We can use the Punnett square shown below:
• +ΔH and +ΔS → spontaneous only at high temperatures• +ΔH and –ΔS → non-spontaneous at all temperatures• –ΔH and +ΔS → spontaneous at all temperatures• –ΔH and –ΔS → spontaneous only at low temperatures
Given:
+ΔH → negative value-ΔS → positive value
• +ΔH and –ΔS → the reaction is nonspontaneous at all temperatures
But if the reaction is in the reversed, ΔH and ΔS would have an opposite sign.
• -ΔH and +ΔS → the reaction is spontaneous in direction at all temperatures
Therefore, the reaction is d.) spontaneous in reverse direction at all temperatures.
What can be said about an endothermic reaction with a negative entropy change?
Frequently Asked Questions
What scientific concept do you need to know in order to solve this problem?
Our tutors have indicated that to solve this problem you will need to apply the Spontaneous Reaction concept. You can view
video lessons to learn Spontaneous Reaction
Or if you need more Spontaneous Reaction practice, you can also practice
Spontaneous Reaction practice problems
.
Spontaneous Reaction Video Lessons
Concept
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