1.00 M lead (II) nitrate solution mean one mole of Pb(NO3)2 in one litre of water (Solvent). One mole of Pb(NO3)2 is equal to 331.2 g.
In order to calculate individual ions molarity, use coefficients
from the balanced dissolution equation.
Pb(NO3)2 = Pb2+ + 2NO3-
e.g. for nitrate ions molarity
(1 mole Pb(NO3)2 /1 liter soln) x(2 mole NO3-/1 mole Pb(NO3)2 )
= 2 mole NO3- / 1 L soln. or 2 M NO3-
Hope it will help.