The number of moles of \( \mathrm{NH_3} \), that must be added to \( 2 \, \text{L} \) of \( 0.80 \, \text{M} \) \( \mathrm{AgNO_3} \) in order to reduce the concentration of \( \mathrm{Ag^+} \) ions to \( 5.0 \times 10^{-8} \, \text{M} \) \( (K_{\text{formation}} \text{ for } [\mathrm{Ag(NH_3)_2}]^{+} = 1.0 \times 10^{8}) \) is __________. (Nearest integer)
[Assume no volume change on adding \( \mathrm{NH_3} \)]
