Leаd iоns cаn be precipitаted frоm aqueоus solutions by the addition of aqueous iodide: Pb2+(aq) + 2I-(aq) → PbI2(s) Lead iodide is virtually insoluble in water so that the reaction appears to go to completion. How many millilitres of 3.550 mol L-1 HI(aq) must be added to a solution containing 0.700 mol of Pb(NO3)2 (aq) to completely precipitate the lead?