Suppose you do not know the enthalpy of decomposition of the process:

Question

CaCO3 = CaO + CO2
Explain in terms of thermodynamic parameters why heating to a high temperature might turn this decomposition to a spontaneous process.

Answer 1

Since a solid is forming a gas, the dS will increase.
dStotal = dSsys + dSsurroundings.
dSsurrounds = -dH/T
As T increases, dS surroundings becomes less; therefore, at some point T will be high enough for the reaction to become spontaneous.

Answer 2

How Do you do ionic compunds with oxyacids