We’re being asked to predict the sign of the entropy change (ΔS) for the given reactions. 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.
Which of the following processes would you expect to have a negative value for entropy?
NaCl(s) → Na+(aq) + Cl- (aq)
2 Al(s) + 3Br2(l) →2AlBr3(s)
C2H5OH(l) → C2H4(g) + H2O(g)
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