A recent investigation of the complexation of SCN with Fe led to values of 125, 20 and 1.0 for , and — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

The overall formation constant ($\beta_3$) for the complex $\text{Fe(SCN)}_3$ is the product of its stepwise formation constants: $\beta_3 = K_1 \times K_2 \times K_3 = 125 \times 20 \times 1.0 = 2500$. The overall dissociation constant is the reciprocal of the overall formation constant: $K_d = \frac{1}{\beta_3} = \frac{1}{2500} = 4.0 \times 10^{-4}$.