[PolloChief]

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.

[Meter]

What is the relationship between Gibbs free energy and spontaneity? How would you calculate it?

[PolloChief]

∆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.

[Orcio_87]

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.

[PolloChief]

Yeah I know that much, it's just that I don't know if this reaction is consuming or emitting heat.

[Borek]

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 B

and

A B + 100kJ

?

[PolloChief]

I get confused on which is which everytime when I see the KJ in the reaction. So I'm not sure.

[Borek]

Heat is either on the left (consumed) or on the right - produced.