Question

Predict the sign of the entropy change, ΔS^∘, for each of the reaction displayed.
[Negative or Postive sign]

CH3OH (l) --> CH3OH (g)
2KIO3 (s) --> 2KCl (s) + 3O2 (g)
2H2 (g) + O2 (g) --> 2H2O(l)
Pb ^2+ (aq) + 2Cl^- (aq) --> PbCl2 (s)

Answer 1

for the reaction CH3OH(l) ----> CH3OH(g) entropy change is +ve since delS= Q/T and heat has to be added to CH3OHb (l) for it to become vapor.

There will be an increase in entropy since gases will have more disorder than solid and entropy is degree of disorder. Hence 2KClO3-(s)---> 2KCl(s)+ 3O2(g)

entropy increases

for the reaction 2H2(g)+ O2(g)----> 2H2O (l) entropy decreases since product is liquid and liqud is more ordered than gas

for the reaction Pb+2 +2Cl(aq)----> PbCl2   entropy decreases