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# Complex Ions: Formation Constant

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Sections
Intro to Buffers
Henderson-Hasselbalch Equation
Intro to Acid-Base Titration Curves
Strong Titrate-Strong Titrant Curves
Weak Titrate-Strong Titrant Curves
Acid-Base Indicators
Titrations: Weak Acid-Strong Base
Titrations: Weak Base-Strong Acid
Titrations: Strong Acid-Strong Base
Titrations: Diprotic & Polyprotic Buffers
Solubility Product Constant: Ksp
Ksp: Common Ion Effect
Precipitation: Ksp vs Q
Selective Precipitation
Complex Ions: Formation Constant

Complex Ion is a structure containing a metal cation that acts as a Lewis Acid.

Concept #1: Complex Ion and Ligand

Formation Constant (Kf): a ratio of product to reactant concentrations.

Example #1: The formation of the complex ion created from the combining of silver ion and cyanide ion is given below:

Ag+ (aq) + 2 CN (aq) ⇌ Ag(CN)2 (aq)  Kf = 1.0 x 1021

If 100.0 mL of 0.0120 M AgClO4 is mixed with 220.0 mL of 0.25 M CN, what is the [Ag+] once equilibrium has been reached?

Practice: If your equilibrium constant K is equal to the product of Ksp and Kf, find the solubility of AgCl in 2.0 M NH3. Ksp of AgCl = 1.77 × 1010; Kf of Ag(NH3)2+ = 1.7 × 107.

Practice: A solution is composed of 3.20 × 104 M Co(NO3)3 mixed with 0.200 M NH3. Determine the [Co3+] that remains once the solution reaches equilibrium in the formation of Co(NH3)63+.