Which of the following changes has a decrease in entropy?

Question

anonymous · Answer

hg N2O4 (g)  2NO2 (g) 
   3O2 (g) + 2KCl (s)  2KClO3 (s) 
   C2H5OH (l) + 3O2 (g)  2CO2 (g) + 3H2O (g) 
   H2O (l)  H2O (g)

mani_jha · Answer

Do you know what a decrease in entropy means?

anonymous · Answer

Yes. It means that the amount of randomness decreases eighter by the movement or amount of moleues

anonymous · Answer

But its hard to tell from these equATIONS

mani_jha · Answer

Now, see if I lump two free molecules(which had a lot randomness) into a single molecule of more weight, which will have more entropy(randomness), the two free molecules, or the resultant single heavier molecule?
Did you get my question?

anonymous · Answer

Uhh. are you asking which would be heavier

anonymous · Answer

I get what you're saying in the first half but when you asked it looks like you left out th word "what" so I couldn't really see what you are asking

mani_jha · Answer

No, I am asking which one will move more easily i.e which will have more randomness. Of course, the single molecules formed as a product will be heavier than either of the reactants.

anonymous · Answer

Is it this one? 3O2 (g) + 2KCl (s)  2KClO3 (s)

mani_jha · Answer

Yes. Do you understand why? 
Two reactants combine to form a single product of more weight. This restricts movement.(It is difficult for a heavier particle to move). So, it has less entropy

anonymous · Answer

OHhh I got ya. So if it decreases we are looking for more of a solid or a more combined molecule. And if it increases we are looking for more seperation. Is this right>

mani_jha · Answer

Yes, exactly.

anonymous · Answer

one thing...Which of the following changes will always be true for a spontaneous reaction?
Would this be 1deltaG

anonymous · Answer

Im sorry -1deltaG

mani_jha · Answer

Yes, whenever Gibb's Free Energy is negative, the reaction is spontaneous. Because then the change in enthalpy is negative. This means that the products are more stable than the reactants.

anonymous · Answer

And would boiling water be an example of an increase in entropy? or these filtering sand out of a sample of water 
   synthesizing water from hydrogen and oxygen

mani_jha · Answer

Boiling water converts liquid water into gaseous water vapour. As the particles in a gas have more randomness, there is an increase in entropy.
Synthesizing water from hydrogen and oxygen is again one case where two molecules lump together to form a heavier molecule. So what do you think?