[nepenthean]

I calculated this, and it must be positive number insofar as it is a decomposition reaction. Yet, the answer key says -431 kcal. Please help. Also, if i wanted to figure out  how much heat is evolved per mole of gas formed in this reaction, how would i start?

Appreciates.

[Dan]

I calculated this, and it must be positive number insofar as it is a decomposition reaction.

Why do you think all decomposition reactions are endothermic? Does the decomposition of nitroglycerine release heat or consume heat?

if i wanted to figure out  how much heat is evolved per mole of gas formed in this reaction, how would i start?

Start by writing a balanced chemical equation.

[nepenthean]

           Why do you think all decomposition reactions are endothermic? Does the decomposition of nitroglycerine release heat or consume heat?

Well, for one, my prof said so. He said you can look at a reaction and, if it is decomp, conclude its endothermicity insofar as the bonds must be broken. Do not bonds need energy to be broken?

I did balance the equation. When I divided his correct answer by number of moles of gas on product side, I do not get the answer provided.

I understand you are not here to do my homework. I can guess folks come here for you to proffer answers to questions they need to figure out. But I come here as a last resort.

[Borek]

He said you can look at a reaction and, if it is decomp, conclude its endothermicity insofar as the bonds must be broken. Do not bonds need energy to be broken?

Take a look at products - they contain very stable molecules like H₂O and CO₂. Some bonds were destroyed, others were created.

[nepenthean]

Yes, I saw that. I do not understand why my prof said you could take a look at a decomp reaction and conclude its endothermicity. Also, I looked online at the reaction. Some say CO is formed not CO2.

[Borek]

I doubt it goes according to one simple equation, most likely you get mixture of mechanisms and products.

[Dan]

I did balance the equation. When I divided his correct answer by number of moles of gas on product side, I do not get the answer provided.

If you show your working we may be able to see why you are getting it wrong.