Which of the following changes has a decrease in entropy?

a. N2O4 (g)yields 2NO2 (g)
b. C2H5OH (l) + 3O2 (g)yields 2CO2 (g) + 3H2O (g)
c. 3O2 (g) + 2KCl (s)yields 2KClO3 (s)
d. H2O (l)yields H2O (g)

Question

Which of the following changes has a decrease in entropy?

a. N2O4 (g)yields 2NO2 (g)
b. C2H5OH (l) + 3O2 (g)yields 2CO2 (g) + 3H2O (g)
c. 3O2 (g) + 2KCl (s)yields 2KClO3 (s)
d. H2O (l)yields H2O (g)

anonymous · Answer

Entropy is randomness or chaos, so which of the choices starts with smaller things to build a larger thing?  That would be the opposite of entropy or would decrease entropy.  It's not the liquid to gaseous water because water in the gaseous form is more random and less ordered and that is more entropy.