Answer is: 18 moles of lead(II)-nitrate.
Balanced chemical reaction:
3Pb(NO₃)₂ + 2AlCl₃ → 2Al(NO₃)₃ + 3PbCl₂.
n(Al(NO₃)₃) = 12 mol.
From chemical reaction: nAl(NO₃)₃) : n(Pb(NO₃)₂) = 2 : 3.
n(Pb(NO₃)₂) = 3 · 12 mol ÷ 2.
n(Pb(NO₃)₂) = 18 mol; amount of substance.
Al(NO₃)₃ is aluminium nitrate.
AlCl₃ is aluminium chloride.
