(NH₄)₃PO₄ is a strong electrolyte which fully dissociates into its ions. The balanced equation for the dissociation is
(NH₄)₃PO₄ → 3NH₄⁺ + PO₄³⁻
The stoichiometric ratio between (NH₄)₃PO₄ and NH₄⁺ is 1 : 3
Hence, moles of (NH₄)₃PO₄ / moles of NH₄⁺ = 1 / 3
moles of (NH₄)₃PO₄ = 3 mol
Hence, moles of NH₄⁺ = moles of (NH₄)₃PO₄ x 3
= 3 mol x 3
= 9 mol
Hence, 3 moles of (NH₄)₃PO₄ give 9 moles of NH₄⁺.