Question

Medals:
Which of the following changes has a decrease in entropy?

Answer 1

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

Answer 2

@studyislandhelp

@ParthKohli

Answer 3

there are several rules to figure out the increase of entropy in a reactions. In your case you can consider the total number of moles before and after the reaction and the change of state of the compound. the entropy increase if the reaction has a bigger number of moles of product respect to the total number of moles of the reactive. for example reaction 1 and 2 the products has more moles than the reactants. the last reaction H2O (l) yields H2O (g), there is a change in the state, the entropy increase if you go from solid<liquid<gas so in this last reaction there is also increase of entropy.
So then the 3O2 (g) + 2KCl (s) yields 2KClO3 (s) is the only reaction in what you will have a decrease in Entropy for the decrease in the number of moles between reactants and products ans also you have a gas in the reactants and only solids in the products.

Answer 4

thanks a lot for the explanation! @Cuanchi

Answer 5

Which of the following processes involves an increase in entropy?

condensing water vapor
melting gold bars
filtering grounds from coffee
freezing popsicles
@Cuanchi

Answer 6

@annas

Answer 7

I would said melting gold bars besides you have to have a lot of money!! the first and the last one are change in the states going from gas to liq and from liq to solid that in both cases decrease the entropy. And I assume that filtering the coffee you go to a more ordered system that decrease the entropy too