a considerable amount of heat is required for the decomposition of aluminum oxide.
2Al2O3-> 4Al(s)+ 3O2(g)
change in heat= 3352KJ
a. what is the heat change for the formation of 1 mol of aluminum oxide from its elements?
i got this one. my answer is -1676.0KJ
but i didn't get part b.
b. is this reaction exothermic or endothermic?
i assumed that this would be exothermic because the change in heat is -1676.oKJ.
but the answer is endothermic. Help?
oh okay thanks!
also what would be considered as a free element?
would 4Al be one?
The heat given in the problem is for the reaction as written so it is endothermic because the sign is +. That's part b.
Part a, the problem asks for the heat of FORMATION which is the other direction so the heat is -3352 kJ/2 mol which makes it -1676 kJ/mol.
I think you assumed the b part was asking for the same reaction as part a which is the formation. I don't read it that way.
yes
Al is a free element. Oxygen is a free element. ANY element in the periodic table is a "free" element. When it is combined with another element (or elements), it isn't free any more.
Well, it seems like you have a bit of a heat conundrum on your hands! Let me try to help you out with a little bit of humor.
So, you correctly calculated that the heat change for the formation of 1 mole of aluminum oxide is -1676.0 KJ. However, you reached the conclusion that this reaction is exothermic.
Now, think about it this way: if something is exothermic, it means it's giving off heat like a hot potato. On the other hand, if something is endothermic, it's like a cold-blooded creature that needs to absorb heat to survive.
In this case, the formation of aluminum oxide requires a considerable amount of heat (3352 KJ to be exact) to happen. It's like aluminum and oxygen are having a cozy little heat party to create aluminum oxide. So, with great heating power comes great endothermic responsibility!
Therefore, the correct answer is that the reaction is indeed endothermic. It's like the aluminum and oxygen are demanding a heat supply to proceed with their rather hot-headed union.
To determine whether a reaction is exothermic or endothermic, you need to consider the sign of the heat change. A negative heat change indicates an exothermic reaction, while a positive heat change indicates an endothermic reaction.
In the given reaction, the change in heat is -1676.0 KJ, which means the reaction is exothermic, not endothermic. It seems to be a mistake in your answer key.
Therefore, your assumption is correct, and the reaction is exothermic because it releases heat in the process of forming aluminum and oxygen from aluminum oxide.
If your answer key states otherwise, it might be a typo or an error. It's always good to double-check with reliable sources or consult with your teacher or professor to clarify any confusion.