00:01
In this problem, we're calculating the change in entropy for several different chemical reactions.
00:07
So how we do that in general is we subtract the total entropy of the reactants from the total entropy of the products.
00:14
So for this first question, we have the decomposition of manganese dioxide into solid manganese and oxygen gas.
00:24
So i have a table or a chart here in the bottom right corner with all of the compounds, in this problem and their corresponding entropy values.
00:35
So we can set this up by, we have one mole, we have to add up the entropy of the product.
00:45
So we have one mole of the solid manganese, which has an entropy value from the chart of 32 joules per kelvin mole.
00:58
And then we also have one mole of oxygen.
01:03
And this has an entropy of 205 .2.
01:10
And then we subtract the entropy of the reactants, which is just the manganese dioxide.
01:16
So again, we have one mole of that, and this has an entropy of 53 .05.
01:30
So once we calculate all of this, we end up with 184 .15 joules per kelvin.
01:42
So that's the first problem.
01:44
The second problem is, i mean, all these problems are basically the same strategy.
01:49
So we're going to take the products.
01:54
We have two moles this time of hydrogen bromide, which has an entropy from the chart of 198 .7.
02:08
And then we subtract the products, or the reactants.
02:13
So we want to add up the reactants here.
02:15
So we have one mole hydrogen gas.
02:21
And this has an entropy of 130 .7.
02:24
And then we have one mole of liquid bromine.
02:46
And this gives us 11 .47...