Explanation
For a spontaneous process the randomness of the molecules in the system increases so the entropy change of the system and surroundings must be positive.
Hence option B is correct.
CH4+2O2→CO2+2H2O(g)+210.8kcal
Then the possible heat of formation of methane will be
CH4+2O2→CO2+2H2O(g); ΔHR=+210.8kcal (iii)
ΔHR for reaction (iii) can be written as:
ΔH=ΔHf(CO2)+2×ΔHf(H2O)−ΔHF(CH4)−2×ΔHf(O2)
⟹210.8=94.2+2×68.3−ΔHf(CH4)−2×0
ΔHf(CH4)=20 kcal
Hence, Option "B" is the correct answer.
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