Predict whether the following reactions would be spontaneous or not under standard conditions or if it's impossible to tell.
2 KClO3(s) + 3 C(s) --> 3CO2(g) + 2KCl(s) Exothermic
2 NO(g) + O2(g) --> 2NO2(g)
Exothermic
H2(g) + Zn(ClO3)2(s) --> 2HClO3(l) + Zn(s) Endothermic
I'm having trouble in trying to figure out if they are spontaneous or not. I understand that if it's exothermic, they are usually spontaneous, but with the given data, I am just unsure.
4 answers
That is right about delta H. The problem is that no data are given for delta S. You can guess about delta S, however, and be close usually. For example, #1: you have solids on the left (reactants) and gas on the right so delta S must be + (more disorder in gases than solids) so we would guess with dH - and dS +, dG would be - and reaction spontaneous. Do 2 and 3 the same way. 2 you have 3 mols gases going to 2 of gases so dS is -. #3 you have gas on left goig tro liquid on right. dS will be -.
I have a question about the format of the problem itself. So it's asking to predict whether the reactions are spontaneous or not, so should I just write spontaneous/non spontaneous, or write that with an explanation?
I don't know the instructions given. If the instructions suggest an explanation then you should giver one; otherwise, I would just write spontaneous or non-spontaneous.
Coolio! Thanks for the help Doc!