$$ \ text {pb (no} _3 \ text {)} _ 2 \ text {(aq) + 2nh} _3 \ text {(aq)} \ rightleftharpoons $$ $$ \ text {[pb (nh} _3 \ text {) _ 2] { + _ + _ {aq)} \ text {2no} _3^-_ {(aq)} $$
$$ \ text {pb (no} _3 \ text {)} _ 2 \ text {(aq) + 2nh} _3 \ text {(aq)} \ rightleftharpoons $$ $$ \ text {[pb (nh} _3 \ text {) _ 2] { + _ + _ {aq)} \ text {2no} _3^-_ {(aq)} $$