The thermal decomposition of calcium carbonate is a classic heterogeneous…

CHEMISTRY · Multi-part · AP · Chemistry · Equilibrium · Equilibrium

Problem

The thermal decomposition of calcium carbonate is a classic heterogeneous equilibrium:

\text{CaCO}_3(s)\rightleftharpoons\text{CaO}(s)+\text{CO}_2(g)

An evacuated reaction vessel containing a lump of

\text{CaCO}_3

is heated to 800 °C. At equilibrium, the measured partial pressure of

\text{CO}_2

is 0.256 atm. Ideal-gas behavior may be assumed. (a) Construct the correct expression for the equilibrium constant

K_p

for this reaction. (b) Calculate the numerical value of

K_p

at 800 °C. (c) Convert the result from part (b) to the corresponding concentration-based constant

K_c

at 800 °C. Show your work explicitly. (d) Explain why the masses of

\text{CaCO}_3

and

\text{CaO}

present in the vessel are irrelevant to the numerical value of the equilibrium constant.