Question

Calculate the concentration of all species of significant concentrations present in 0.1 M H₃PO₄ solution. K₁ = 7.5 x 10^–3, K₂ = 6.2 x10^–8, K₃ = 3.6 x10^–3. 

Answer 1

The value of K₁ is much large than K₂ and K₃. Also dissociation of II and III steps occurs in presence of H⁺ furnished in I step and thus, dissociation of II and III steps is further suppressed due to common ion effect.

The dissociation of H₂PO^-₄  occurs in presence of [H⁺] furnished in step I.