For a particular reversible reaction at temperature `T, DeltaH` and `DeltaS` were found to be both `+ve`. If `T_e` is the temperature at equilibrium, the reaction would be spontaneous when :
For a particular reversible reaction at temperature `T, DeltaH` and `DeltaS` were found to be both `+ve`. If `T_e` is the temperature at equilibrium, the reaction would be spontaneous when :
A
`T_(e) gt T`
B
`T gt T_(e)`
C
`T_(e)` is 5 times T
D
`T=T_(e)`
Text Solution
AI Generated Solution
The correct Answer is:
To solve the problem, we need to analyze the conditions under which a reversible reaction is spontaneous given that both ΔH (enthalpy change) and ΔS (entropy change) are positive.
### Step 1: Understand the Gibbs Free Energy Equation
The Gibbs free energy change (ΔG) for a reaction is given by the equation:
\[
\Delta G = \Delta H - T \Delta S
\]
Where:
- ΔG = Change in Gibbs free energy
- ΔH = Change in enthalpy
- T = Temperature in Kelvin
- ΔS = Change in entropy
### Step 2: Analyze the Conditions for Spontaneity
A reaction is spontaneous when ΔG < 0. Therefore, we need to find conditions under which:
\[
\Delta H - T \Delta S < 0
\]
Rearranging this inequality gives:
\[
\Delta H < T \Delta S
\]
### Step 3: Relate Temperature to Equilibrium Temperature
At equilibrium, the Gibbs free energy change is zero (ΔG = 0). This leads to:
\[
\Delta H = T_E \Delta S
\]
Where \(T_E\) is the equilibrium temperature. Rearranging this gives:
\[
T_E = \frac{\Delta H}{\Delta S}
\]
### Step 4: Substitute into the Spontaneity Condition
From the spontaneity condition derived in Step 2, we can substitute \(T_E\):
\[
\Delta H < T \Delta S \implies \frac{\Delta H}{\Delta S} < T
\]
This implies:
\[
T_E < T
\]
### Conclusion
Thus, for the reaction to be spontaneous, the temperature \(T\) must be greater than the equilibrium temperature \(T_E\):
\[
T > T_E
\]
### Final Answer
The reaction would be spontaneous when \(T > T_E\).
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