We’re asked to calculate the equilibrium pressure of CO2 at 410°C using standard thermodynamic data for the given balanced reaction:
PbCO3 (s) ⇌ PbO(s) + CO2 (g)
Recall that the equilibrium constant is the ratio of the products and reactants. We use Kp when dealing with pressure
Note that solid and liquid compounds are ignored in the equilibrium expression.
Also, recall that ΔG˚rxn and K are related to each other:
The thermodynamic data ( ΔH˚f and ΔS˚) of each reactant and product can be found in textbooks/online:
S˚ (J/mol • K)
We can use the following equation to solve for ΔG˚rxn:
For this problem we need to do these steps:
Step 1: Calculate ΔH˚rxn.
Step 2: Calculate ΔS˚rxn.
Step 3: Use ΔH˚rxn and ΔS˚rxn to calculate for ΔG˚rxn.
Step 4: Calculate for K (Kp).
Step 5: From Kp, solve for equilibrium partial pressure of CO2
Using data in Appendix C in the textbook, calculate the equilibrium pressure of CO2 in the system at 410 oC.
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