Destroyer G.Chem #22

[hunterpostbacst]

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The orgoman says that since the solution got colder, heat was absorbed, thus, the reaction is endothermic. However, isn't it opposite?
I think the solution got colder, heat was out, thus, the reaction is exothermic. (The solution(system) got colder, but the environment got heated)😕

 

[LoLPoPs]

I think they are right.

The solution temperature decreases. That means solid NH4NO3 took the heat while water lost the heat.

Thus heat is absorbed by the solid. And so it's endothermic. 😍

Hope this makes sense.

 

[hunterpostbacst]

That's what I am confused. If heat was absorbed by the solid while dissolving, isn't it exothermic? When heat added to the water, it's endothermic, I doubt.

 

[llungu]

You have to think about the system and the surroundings separately. If the system/reaction is endothermic, it will absorb heat from the surrounding (ie the solution). This will make the solution colder. Just like if the system (ie the reaction) was exothermic, it would give off heat, making the surroundings/solution hotter.

 

[hunterpostbacst]

In this case, we should see the solution(water) as the surrounding?

 

[llungu]

Yeah the solution would get colder for an exothermic reaction... we have different versions of destroyer, so i'm not sure what the question is asking exactly.

 

[UCB05]

In this case, we should see the solution(water) as the surrounding?

You have to look at the solid->solute dissolution as the system, and the solvent water as the surrounding. The process gains heat and takes it away from its immediate surroundings, the water solvent. Hence the process is endothermic.

 

[GiTsticker]

Alright lemme take a shot at explaining this using physics terminology. Energy is never lost, it only changes form. When the temperature decreases, that means energy in the form of heat was changed into some other energy, in this case bond energy in the molecules. Another thing to consider is that when they measure temps for reactions like these, it's usually done in a bomb calorimeter, so it's not like heat is being let out and everything gets colder. It means that when the reaction takes place INSIDE the calorimeter, the calorimeter and the contents get colder. So that heat isn't being radiated out or something, it's being stored in the bonds of the products.

Yeah the solution would get colder for an exothermic reaction... we have different versions of destroyer, so i'm not sure what the question is asking exactly.

Solution gets warmer in exothermic. Energy is released from bonds in the form of heat which warms the solution.