alleryStart learning →Water appears as a product in a gas phase reaction. Does its concentration enter the Kc expression?
ANo, because water is always left out of Kc
BYes, because here water is not the solvent
CNo, because gases never appear inside Kc
DYes, but only when its coefficient is one
Answer & Solution
Correct answer: B. Yes, because here water is not the solvent
1. Water is omitted from Kc when it is acting as the solvent of a dilute solution.
2. In a gas phase reaction water is not the solvent, and its concentration genuinely changes.
3. Gaseous water is therefore included in the expression like any other gaseous species.
4. The coefficient sets the power on the term, but it does not decide inclusion.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 13 "Fundamental Equilibrium Concepts", section 13.2 Equilibrium Constants_
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