If for a certain reaction rH is 30 kJ mol–1 at 450 K, the value of rS (in JK–1 mol–1) for which the same reaction will be spontaneous at the same temperature is:

1. 70

2. –33

3. 33

4. –70

Subtopic:  Spontaneity & Entropy |
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A reaction, \(A + B \rightarrow C+D - q~ cal. \) is found to have a positive entropy change.
The reaction will be:
1. possible at high temperature. 
2. possible only at low temperatures. 
3. not possible at any temperature. 
4. possible at any temperature.
Subtopic:  Spontaneity & Entropy |
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From NCERT
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For the oxidation of iron,

4Fe(s) + 3O2 (g) →  2Fe2O3 (s)
entropy change is -549.4 JK-1 mol-1 at 298 K.

(rHΘ for this reaction is -1648 × 103 J mol-1)

The reaction is:

1. Spontaneous reaction

2. Non-spontaneous reaction

3. Reaction is an equilibrium

4. Cannot predict

Subtopic:  Spontaneity & Entropy |
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