The reaction of \( \mathrm{Pb(NO_3)_2} \) and \( \mathrm{NaCl} \) in water produces a precipitate that dissolves upon the addition of \( \mathrm{HCl} \) of appropriate concentration. The dissolution of the precipitate is due to the formation of:
\( \mathrm{PbCl_2} \)
\( \mathrm{PbCl_4} \)
\( \left[\mathrm{PbCl_4}\right]^{2-} \)
\( \left[\mathrm{PbCl_6}\right]^{2-} \)
