Question

Which of the following changes has a decrease in entropy?
Answer







C2H5OH (l) + 3O2 (g) 2CO2 (g) + 3 H2O (g)








2LiClO3 (s) 3O2 (g) + 2LiCl (s)








C6H6 (l) C6H6 (s)








N2O4 (g) 2NO2 (g)

Answer 1

the quickest way to determine if entropy increases or decreases in a reaction is to look at the number of molecules that exist in the various phases, (s), (l), or (g). A reaction that takes a liquid and turns it into a gas will have a large increase in entropy:
\[H_2O(l) \rightarrow H_2O(g)\]
a reaction that takes one mole of gas and turns it into two (or more) moles of gas also experiences an increase in entropy:
\[N_2O_4(g) \rightarrow 2NO_2(g)\]
the opposite is also true. A reaction will decrease in entropy if the number of gas molecules decreases, or a reaction takes a very disordered gas and condenses it into a liquid, or solid. From that, which is the best option you see?

Answer 2

D?

Answer 3

try again. option D is an increase in entropy: 1 mole of gas becomes 2 moles of gas

Answer 4

A

Answer 5

still no. It's C
\[C_6H_6(l) \rightarrow C_6H_6(s)\]
is a decrease in entropy because the liquid is becoming more ordered. entroyp is a measure of the "randomness" or "disorder" that a molecule has. A solid has less entropy than that same substance as a liquid, because the molecules of a solid are packed in nice, tight ordered crystals.

Answer 6

Actually that isn't the right answer. I selected that answer the first time and got it wrong, which is why I am asking for help.