We’re being asked to determine the reaction that has ΔS° > 0 at 25°C. Recall that if:
• ΔS > 0 or ΔS = (+); entropy is increased
• ΔS < 0 or ΔS = (–); entropy is decreased
Remember that phase changes lead to a change in entropy:
Also, recall that an increase in the number of gas molecules in the reaction also leads to an increase in entropy.
For which of the following reactions is ∆S° > 0 at 25°C?
A) 2H2(g) + O2(g) → 2H2O(g)
B) 2ClBr(g) → Cl2(g) + Br2(g)
C) I2(g) → I2(s)
D) 2NO(g) + O2(g) → 2NO2(g)
E) NH4HS(s) → NH3(g) + H2S(g)
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