A) 2NO (g) + #O_2# (g) # arr2NO_2# (g)B) #COCl_2# (g) #rarr# CO(g) + #Cl_2# (g)C) #CH_3OH (l) arr# CO(g) + #2H_2# (g)D) #NaClO_3#(s) # arrNa^+# (aq)+#ClO_3^-# (aq)E) nobody of the over will display a decrease in entropy.

You are watching: Which of the following changes has a decrease in entropy?


The entropy that a system increases whenever its corpuscle have much more freedom of motion.

Thus, the entropy increases whenever you have more moles that gaseous assets than that reactants and also whenever friend have more product particles in solution than you have actually of reactant particles.

Conversely, entropy decreases when you have actually the the contrary situations.


#"2NO(g)" + "O"_2"(g)" → "2NO"_2"(g)"#

You have actually 3 mol of gas top top the left and also 2 mol on the right, therefore entropy is decreasing.

This is the exactly answer.


#"COCl"_2"(g)" → "CO(g)" + "Cl"_2"(g)"#

You have 1 mol the gas on the left and 2 mol of gas ~ above the right, so entropy is increasing.

This price is incorrect.


#"CH"_3"OH(l)" → "CO(g)" + "2H"_2"(g)"#

This has actually no moles of gas top top the left and 3 mol the gas top top the right, therefore entropy is increasing.

This prize is incorrect.


#"NaClO"_3"(s)" → "Na"^"+""(aq)" + "ClO"_3^"-""(aq)"#

There are much more particles in systems on the best than on the left, for this reason entropy is increasing.

This price is incorrect.

Answer connect

Apr 28, 2017



A) decrease; much less moles of gas in productB) < no sure, but it doesn"t seem come have changed aside from splitting... Probably increase? there are much more moles in the product... >C) increase; liquid to gas (wow, the went straight past solid... That"s a many entropy isn"t it?)D) increase; solid come aqueous (gas/liquid distributed in solution)

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Stefan V.
Apr 28, 2017

Here"s what i got.


The basic idea here is that entropy increases as disorder and also randomness increase.

Similarly, entropy decreases as disorder and also randomness decrease.

Now, randomness and disorder rise as a problem goes indigenous solid come liquid, and finally come gas. On the other hand, randomness and disorder decrease as a problem goes native gas to liquid, and finally come solid.


So appropriate from the start, you recognize that any reaction that has actually a gas as a reactant and a liquid as a product, because that example, will an outcome in a decrease in entropy.

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In your case, you have

#"CH"_ 3"OH"_ ((l)) -> "CO"_ ((g)) + 2"H"_ (2(g))#

A liquid is gift converted to 2 gases, so entropy will certainly increase.

#"NaClO"_ (3(s)) -> "Na"_ ((aq))^(+) + "ClO"_ (3(aq))^(-)#

A solid is being liquified to develop solvated ions, so in general, you deserve to say that entropy will certainly increase. This is no a very an excellent example since there are solids that can be liquified in water come a decrease in entropy.

I"m not going to enter why that is the case, just keep in mind that it is possible.

Now, the an initial two reactions involve gas reactants and also gaseous products. In together cases, look in ~ the total variety of moles of gas current on the 2 sides that the chemical equation.

When it pertains to reactions the involve gases, you will certainly have

#"more mole of gas on the reactants" next " -> " decrease in entropy"##"more mole of gas on the products" side " -> " rise in entropy"#

Notice that this reaction

#2"NO"_ ((g)) + "O"_ (2(g)) -> 2"NO"_ (2(g))#

has a complete of #3# moles the gas top top the reactants" side and also only #2# moles the gas top top the products" side.