00:01
All right, so we have a thermochemical equation here that's balanced and we have our delta h.
00:05
First we want to know is it exo or endothermic.
00:08
So to identify that, we look at the sign, positive or negative for delta h, in this case it's negative, so that corresponds to an exothermic reaction.
00:16
And if it was positive, it would be endothermic.
00:19
Negative or exothermic, heat means that a heat is released in the process of this reaction.
00:26
Okay, what is the delta h for the reverse reaction? so the delta h reverse is simply we take the delta h for the reaction and we flip the sign.
00:35
In this case, it's going to be positive.
00:38
Oops, 20 .2 kilojoules.
00:45
All right.
00:46
Now, if we have 3 .2 moles of s8 reacting, what is the delta? so the thermochemical equation says that we have negative 20 .2 kilojoules are associated with an eighth of a mole of s8.
01:06
So basically we use dimensional analysis or erration.
01:09
Or whatever, and we can get the proportional amount of heat for 3 .2 moles.
01:13
So then we have, we can put on our calculator, 3 .2 times negative 20 .2, and then times 8, or divided by 1 8...