# How can I write the solubility equilibrium equation?

Apr 18, 2015

Ksp = (${\left[P o s i t i v e I o n\right]}^{n}$ x ${\left[N e g a t i v e I o n\right]}^{n}$) divide by [Compound]

n is the number of moles and most of the time concentration of the compound isn't involved in the equation because solids and liquids are emitted from the Equilibrium equation.

E.g Solubility of NaCl will be:

Ksp = ${\left[N {a}^{+}\right]}^{1}$ x ${\left[C {l}^{-}\right]}^{1}$

No dividing by the [Compound] because NaCl is a solid, so it doesn't take part.

• Square brackets [ ] indicate concentration

Hope I helped :)