A solution is \(1 \times 10^{-4} M\) in \(\mathrm{NaF}, \mathrm{Na}_{2}
\mathrm{S},\) and \(\mathrm{Na}_{3} \mathrm{PO}_{4} .\) What would be the order
of precipitation as a source of \(\mathrm{Pb}^{2+}\) is added gradually to the
solution? The relevant \(K_{\mathrm{sp}}\) values are
\(K_{\mathrm{sp}}\left(\mathrm{PbF}_{2}\right)\) \(=4 \times 10^{-8},
K_{\mathrm{sp}}(\mathrm{PbS})=7 \times 10^{-29},\) and
\(K_{\mathrm{sp}}\left[\mathrm{Pb}_{3}\left(\mathrm{PO}_{4}\right)_{2}\right]=\)
\(1 \times 10^{-54}\).