The $25 \,mL$ of a $0.15 \, M$ solution of lead nitrate, $Pb \left( NO _{3}\right)_{2}$ reacts with all of the aluminium sulphate, $Al _{2}\left( SO _{4}\right)_{3}$, present in $20 \,mL$ of a solution. What is the molar concentration of the $Al _{2}\left( SO _{4}\right)_{3}$ ? $3 Pb \left( NO _{3}\right)_{2}( aq )+ Al _{2}\left( SO _{4}\right)_{3}( aq ) \longrightarrow 3 PbSO _{4}( s )+2 Al \left( NO _{3}\right)_{3}( aq )$