Problem: Which of the following processes would you expect to have a negative value for entropy? NaCl(s) → Na+(aq) + Cl- (aq) H2O(s) →H2O(l) NaCl(s) →NaCl(l) 2 Al(s) + 3Br2(l) →2AlBr3(s) C2H5OH(l) →  C2H4(g) + H2O(g)

FREE Expert Solution

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.


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Problem Details

Which of the following processes would you expect to have a negative value for entropy? 

NaCl(s) → Na+(aq) + Cl- (aq) 

H2O(s) →H2O(l) 

NaCl(s) →NaCl(l) 

2 Al(s) + 3Br2(l) →2AlBr3(s) 

C2H5OH(l) →  C2H4(g) + H2O(g)

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