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Topic: endothermic reaction  (Read 592 times)

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Offline juson

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endothermic reaction
« on: October 31, 2023, 09:48:53 AM »
I have a question about the mark scheme for an exam question about an endothermic reaction. The graph shows temperature decreasing, then increasing again once the reaction is finished. The mark scheme says the reason for the increase is because energy is transferred to the solution from the surroundings. I thought that this would make the surroundings cooler, so the temperature would decrease? It’s really annoying me that I can’t wrap my head around this point.

Offline Borek

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Re: endothermic reaction
« Reply #1 on: October 31, 2023, 03:23:04 PM »
Surroundings are in general infinite, so even if the reaction cools immediate surroundings for a moment, heat will flow back till the temperature of the mixture is back to the ambient temperature.
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Offline gavindor

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Re: endothermic reaction
« Reply #2 on: November 12, 2023, 08:23:07 PM »
I have a question about the mark scheme for an exam question about an endothermic reaction. The graph shows temperature decreasing, then increasing again once the reaction is finished. The mark scheme says the reason for the increase is because energy is transferred to the solution from the surroundings. I thought that this would make the surroundings cooler, so the temperature would decrease? It’s really annoying me that I can’t wrap my head around this point.

i'm no expert but

You write "The graph shows temperature decreasing"  <--  I guess you mean temperature of the solution

You write (presumably about the tempreature of the solution) "then increasing again once the reaction is finished. "

You write "The mark scheme says the reason for the increase is because energy is transferred to the solution from the surroundings."

This is clearly the case. If the temperature of the solution increased, then the heat came from the surroundings into it.  If the temperature of the solution decreased, the heat went from the solution to the surroundings.

If heat energy is transferred from A to B, then B increases in heat(gets hotter). And A decreases in heat (gets cooler).

Often endothermic and exothermic is described more in terms of energy generally, and the system is the interactions and the surroundings would be the solution and everything outside the solution.  But in your case, the system is the solution and the surroundings is outside of it. And it's talking of heat transfer between solution and surroundings of the solution.

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