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Topic: A Gibb's problem  (Read 680 times)

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Offline PolloChief

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A Gibb's problem
« on: June 01, 2021, 03:02:28 PM »
The question is this:
CaCO3+179.2KJ --->CaO (s)+ O2 (g)

A) The reaction is spontaneous in high temperatures.
B) The reaction is spontaneous in Low temperatures.
C) Is always spontaneous.
D) Is always Non-spontaneous.

I chose option A, but can't find the answer in my textbook.

Offline Meter

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Re: A Gibb's problem
« Reply #1 on: June 01, 2021, 03:27:27 PM »
What is the relationship between Gibbs free energy and spontaneity? How would you calculate it?

Offline PolloChief

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Re: A Gibb's problem
« Reply #2 on: June 02, 2021, 01:07:37 PM »
∆G=∆H-T∆S
∆H is Enthalpy
T is temperature
∆S is Entropy (or change in entropy).

In this question, entropy is (+) because the product has more moles and a change in state (s-->g).
But I don't know if ∆H is (+) or (-).
If ∆G=+
Then it's Non-spontaneous.
If ∆G=-
Then it's spontaneous.

Online Orcio_Dojek

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Re: A Gibb's problem
« Reply #3 on: June 02, 2021, 01:25:32 PM »
Quote
But I don't know if ∆H is (+) or (-).

CaCO3 + 179.2 kJ ---> CaO (s)+ CO2 (g)

Positive enthalpy means that reaction consumes heat, negative - heat is emmited.

Offline PolloChief

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Re: A Gibb's problem
« Reply #4 on: June 03, 2021, 06:17:55 AM »
Yeah I know that much, it's just that I don't know if this reaction is consuming or emitting heat.

Online Borek

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Re: A Gibb's problem
« Reply #5 on: June 03, 2021, 08:17:57 AM »
Yeah I know that much, it's just that I don't know if this reaction is consuming or emitting heat.

Do you see a difference between

A + 100kJ :rarrow: B

and

A :rarrow: B + 100kJ

?
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Offline PolloChief

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Re: A Gibb's problem
« Reply #6 on: June 04, 2021, 05:55:06 AM »
I get confused on which is which everytime when I see the KJ in the reaction. So I'm not sure.

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Re: A Gibb's problem
« Reply #7 on: June 04, 2021, 08:03:11 AM »
Heat is either on the left (consumed) or on the right - produced.
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