[MIA6]

So I know that endothermic reaction is taking in heat and exothermic reaction is heat going out. Plus, my understand of equilibrium is if one molecule contains too much heat, then it lets out some to the environment. If environment has more heat, then molecules absorbs some. However, it may not be the case. For example, N2+3H2-->2NH3+Heat
In the change in temperature, if temperature is increasing, then it's from right to left, and it's endothermic. BUT WHY?! First, when it says temperature is increasing, does it mean temperature in the molecule? If so, then molecule will give out heat to the environment, and thus exothermic,from left to right. It's very common sense. But I just don't get why it's the other way around.
Thank you.

[Astrokel]

I believe it is the surrounding temperature. Of course this is translated to thermal energy for the molecules to have higher average KE, thus increasing the frequency of effective of collision, in other way, more molecules reaching the activation energy. As the word suggests, in an equilibrium system, a change in temeprature will distort this 'balanced' system, thus of course this system will try to counteract the change by going opposite. In your example, Haber process, rememeber, it is an equilibrium system, though forward reaction is an exothermic reaction, backward reaction(endothermic) is also at the same rate as the forward.

Note it is pretty wrong to say one molecule contain too much heat than environment then it let out some because it really depends on the formation of products.

I hope i understood your question correctly.

[MIA6]

If it is the surrounding temperature, then when T increases, it gives out heat to the molecule? I know it's an equilibrium system, and if one changes, the other counteract to balance again, but understanding doesn't work in this case. Can you use my example to explain the problem to me:  N2+3H2-->2NH3+Heat

[Astrokel]

The problem is i don't quite understand what you are asking.

[Vidya]

when we use exo or endo terms it means heat is given off or taken off from the surroundings .
If you raise the temperature then equilibrium will shift to consume that extra heat.So  reactions will shift in the direction of endothermic reactions.

[MIA6]

when we use exo or endo terms it means heat is given off or taken off from the surroundings .
If you raise the temperature then equilibrium will shift to consume that extra heat.So  reactions will shift in the direction of endothermic reactions.

I know that when temperature is increasing, equilibrium will shift to consume/ let out the extra heat, then is that exothermic since it means takes off heat? and when it says temperature is increasing, it means surrounding temperature?

[Vidya]

yes temperature of surroundings including the system.

[MIA6]

yes temperature of surroundings including the system.

So then can I consider surrounding is part of the system, and molecules are also part of system?

[Vidya]

Molecules are the part of the system.System and surrounding is the universe.Vessel in which reaction is carried out is called system .During exo and endo reaction heat or temperature of the system changes .Change in temp of the surroundings depend on the nature of system --like in isolated system there is no change in temp of the surroundings.

[MIA6]

So if the temperature of the surrounding increases, then the heat from the surrounding is likely to give heat to the molecules, so in molecules' perspective, it's endothermic, which is taking in the heat from surrounding? N2+3H2-->2NH3+Heat, in this case, the original molecule/reactant is 2NH3, and then it takes in heat, and produces the other two molecules, which are N2 and 3H2? Is my understanding correct?

[Donaldson Tan]

Let's put it this way. You have a system of gas molecules in chemical equilibrium. The forward reaction is exothermic while the backward reaction is endothermic. When you apply heat to the system, Le Chatelier's Principle implies that the system will act to remove the heat, thus the endothermic reaction is favoured. When you remove heat from the system, Le Chatelier's Principle implies that the system will act to compensate the heat loss, thus the exothermic reaction is favoured.

[MIA6]

Let's put it this way. You have a system of gas molecules in chemical equilibrium. The forward reaction is exothermic while the backward reaction is endothermic. When you apply heat to the system, Le Chatelier's Principle implies that the system will act to remove the heat, thus the endothermic reaction is favoured. When you remove heat from the system, Le Chatelier's Principle implies that the system will act to compensate the heat loss, thus the exothermic reaction is favoured.

I understand the theory, but don't you think it's contradicting itself when you say "the system will act to remove the heat, thus the endothermic reaction is favored"? because we know that endothermic means to take in the heat, if you want to remove the heat, then why it's endo, is that supposed to me exothermic, which literally means to remove the heat as you said before?

[Astrokel]

if you want to remove the heat, then why it's endo,

Isn't endothermic taking in heats; helping to remove heat from the system? You have to remember that both forward(exo) and backward(endo) reaction is occuring at equal rate.

but don't you think it's contradicting itself when you say

This is because you are distorting this balanced system. The system will act to take in heats so as to re-establish the equilibrium system by favouring backward reaction. It all makes sense and is very true even in industrial production especially your case on Haber Process.

[MIA6]

if you want to remove the heat, then why it's endo,

Isn't endothermic taking in heats; helping to remove heat from the system? You have to remember that both forward(exo) and backward(endo) reaction is occuring at equal rate.

but don't you think it's contradicting itself when you say

This is because you are distorting this balanced system. The system will act to take in heats so as to re-establish the equilibrium system by favouring backward reaction. It all makes sense and is very true even in industrial production especially your case on Haber Process.

Oh, I think I get it. It's just since the system wants to remove the heat, so molecules take in heat by endothermic.  and molecules are also part of the system, right? coz I am kinda confused with what 'system' really refers to when people say it.

[Astrokel]

Yes you are right molecules are part of the system and also the spaces it occupied. It's very important to define your system right especially in Physics.