The effect of temperature on spontaneity of reactions are represented as :
| H | S | Temperature | Spontaneity | |
|---|---|---|---|---|
| (A) | any T | Non spontaneous | ||
| (B) | low T | spontaneous | ||
| (C) | low T | Non spontaneous | ||
| (D) | any T | spontaneous |
The incorrect combinations are :
- A(A) and (C) only
- B(B) and (D) only
- C(A) and (D) only
- D(B) and (C) only
View written solutionFree
Correct answer: D
We use the spontaneity criterion:
A reaction is spontaneous when:
Now check each combination.
1. Case (A):
Then
So is always positive for any . Hence the reaction is non-spontaneous at any temperature.
So (A) is correct.
2. Case (B):
Then
At low , the term dominates, so . At high , the term can dominate, so .
Therefore this reaction is spontaneous at high temperature, not low temperature.
So (B) is incorrect.
3. Case (C):
Then
At low , the negative term dominates, so . At high , the positive term can dominate, so .
Therefore the reaction is spontaneous at low temperature. The table says low , non-spontaneous, which is wrong.
So (C) is incorrect.
4. Case (D):
Then
Both terms make negative for all temperatures. So the reaction is spontaneous at any temperature.
So (D) is correct.
5. Incorrect combinations
The incorrect rows are:
- (B)
- (C)
Hence the correct option is:
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