Sample 1Medium
For a reaction ΔH = +30 kJ mol^-1 and ΔS = +100 J K^-1 mol^-1. Assuming both are independent of temperature, above what temperature does the reaction become spontaneous?
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The answer is C.
The reaction is spontaneous when ΔG = ΔH − TΔS < 0, that is when T > ΔH/ΔS. T = 30000 J mol^-1 / 100 J K^-1 mol^-1 = 300 K.
- A.
This divides 30 by 100 without converting kJ to J.
- B.
This multiplies the kJ-to-J factor in the wrong direction (30000/10).
- D.
This uses 3000 J instead of 30000 J for ΔH.
NCERT: Class 11 Chemistry, Chapter 5, 5.6