Equilibrium and thermodynamics

[erisedk]

Homework Statement

The thermal dissociation equilibrium of CaCO₃ (s) is studied under different conditions.
CaCO₃ ⇔ CaO (s) + CO₂ (g)
For this equilibrium, the correct statement(s) is (are)
(A) ΔH is dependent on T
(B) K_eq is independent of the initial amount of CaCO₃
(C) K_eq is dependent on the pressure of CO₂ at a given T
(D) ΔH is independent of the catalyst, if any

Answers are (A), (B) and (D)

Homework Equations

The Attempt at a Solution

I need someone to tell me if my justification for (A) is correct, and clear a doubt I have on (C).

For (A), since this reaction is taken to be at equilibrium ΔG = 0.
ΔG = ΔH - TΔS
⇒ ΔH = TΔS (at eq)
Since ΔH ∝ T
(A) is correct.

I'm asking this because I think my reasoning might be wrong as I saw a justification involving Kirchhoff's law, http://chemwiki.ucdavis.edu/Core/Ph...namics/State_Functions/Enthalpy/Kirchhoff_Law

For (C), I'm well aware that equilibrium constants are independent of concentrations of reactants and products, and they are a fixed value for a given reaction at a given temperature.
However, I'm unable to reason why this is so. In this case K_p = (p_co2)^eq, i.e. partial pressure of CO₂ at equilibrium. So isn't is directly dependent on the pressure of CO₂, even though the pressure of CO₂ at equilibrium is a fixed value at a given temperature and volume due to ideal gas law?

Thank you!

 

[Ygggdrasil]

Perhaps they meant that K_eq is independent of the starting concentration of CO₂.

 

[Chestermiller]

The reason A is correct can be explained in terms of Hess's Law.

Regarding choice C, I think you're "well aware" explanation is right on target.