The number of moles of $N{H}_3,$ that must be added to 2L of 0.80 M $AgN{O}_3$ in order to reduce the concentration of $A{g}^{+}$ ions to $5.0x{10}^{-8}M$ is $(K_f$ for ${\left[Ag{\left(N{H}_3\right)}_2\right]}^{+}=1.0x{10}^8)$