00:01
So we are to determine the sign of the standard entropy change for the given reactions below.
00:09
So what you have to remember is that the entropy is positive when something goes from a solid to liquid or liquid to gas.
00:20
So from solid liquid to gas, then we'll have positive entropy.
00:32
But if it's the other way from gas to liquid to solid, then we'll have.
00:36
Have negative.
00:39
This is positive here.
00:42
So from solid to liquid to gas, entropy increases.
00:45
So that means we have positive entropy.
00:49
And then if a gas changes to liquid or liquid to solid, then entropy decreases.
00:59
So using this concept, let's evaluate the given equations.
01:04
On the reactant side, we have solid and it produces gas on the product.
01:08
So that means from solid to gas there will be an increase in entropy.
01:16
So that means it's positive b from gas to gas.
01:27
In this case, since they have the same phase, we'll check the number of molecules...