alleryStart learning →Solid lead(II) chloride dissolves as PbCl2(s) forming Pb2+(aq) and 2Cl-(aq). What is Kc?
AKc = [Pb2+] x [Cl-] squared for this
BKc = [Pb2+] x [Cl-] with no powers used
CKc = [Pb2+] x [Cl-]^2 / [PbCl2] here
DKc = [PbCl2] / ([Pb2+] x [Cl-] squared)
Answer & Solution
Correct answer: A. Kc = [Pb2+] x [Cl-] squared for this
1. The solid lead(II) chloride is a pure solid, so it never appears in the expression.
2. Both ions are aqueous, so both belong in the numerator as products.
3. The chloride coefficient is 2, so its concentration is raised to the second power.
4. That gives Kc as the lead ion concentration times the chloride concentration squared.
5. Keeping the solid in the expression, or dropping the square, are the two standard traps.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 13 "Fundamental Equilibrium Concepts", section 13.2 Equilibrium Constants_
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