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) Namong the above will show a decrease in entropy.

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


The entropy of a mechanism boosts whenever before its pposts have even more flexibility of activity.

Hence, the entropy boosts whenever before you have actually more moles of gaseous products than of reactants and whenever you have actually more product pshort articles in solution than you have of reactant particles.

Conversely, entropy decreases when you have actually the opposite cases.


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

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

This is the correct answer.


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

You have actually 1 mol of gas on the left and 2 mol of gas on the ideal, so entropy is increasing.

This answer is incorrect.


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

This has actually no moles of gas on the left and 3 mol of gas on the best, so entropy is increasing.

This answer is incorrect.


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

Tbelow are more pposts in solution on the appropriate than on the left, so entropy is increasing.

This answer is incorrect.

Answer attach

Apr 28, 2017



A) decrease; less moles of gas in productB) < Not sure, however it doesn"t seem to have changed aside from separating... Maybe increase? Tright here are more moles in the product... >C) increase; liquid to gas (wow, it went right past solid... that"s many entropy isn"t it?)D) increase; solid to aqueous (gas/liquid spread in solution)

Answer connect

Stefan V.
Apr 28, 2017

Here"s what I obtained.


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

Similarly, entropy decreases as disorder and randomness decrease.

Now, randomness and disorder boost as a substance goes from solid to liquid, and finally to gas. On the various other hand also, randomness and disorder decrease as a substance goes from gas to liquid, and ultimately to solid.


So right from the begin, you know that any type of reaction that has a gas as a reactant and a liquid as a product, for example, will certainly result in a decrease in entropy.

See more: Why Have All The Rates Of Change In This Assignment Been Negative? Explain.

In your case, you have

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

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

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

A solid is being dissolved to create solvated ions, so in general, you deserve to say that entropy will certainly increase. This is not a very great instance bereason there are solids that have the right to be liquified in water to a decrease in entropy.

I"m not going to go into why that is the situation, just keep in mind that it is possible.

Now, the initially two reactions involve gaseous reactants and also gaseous products. In such situations, look at the total variety of moles of gas existing on the two sides of the chemical equation.

When it concerns reactions that involve gases, you will certainly have

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

Notice that this reaction

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

has actually a total of #3# moles of gas on the reactants" side and also just #2# moles of gas on the products" side.