Equilibrium expressions with solids
What is the equilibrium expression for CaCO3(s) ⇌ CaO(s) + CO2(g)?
Answer B: explanation for every choice
A
Solids are not included.
B
Correct. Pure solids and liquids have an activity of 1 and are left out of the expression.
C
This is inverted and also includes solids.
D
Solids are not included, and CO2 must appear.
TakeawayLeave pure solids and liquids out of K.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp108.