Copper is an excellent electrical conductor widely used in making electric
circuits. In producing a printed circuit board for the electronics industry, a
layer of copper is laminated on a plastic board. A circuit pattern is then
printed on the board using a chemically resistant polymer. The board is then
exposed to a chemical bath that reacts with the exposed copper, leaving the
desired copper circuit, which has been protected by the overlaying polymer.
Finally, a solvent removes the polymer. One reaction used to remove the
exposed copper from the circuit board is
$$
\begin{aligned}
\mathrm{Cu}(s)+\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}(a
q)+4 \mathrm{NH}_{3}(a q) & \longrightarrow \\
& 2 \mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}(a q)
\end{aligned}
$$
A plant needs to produce 5000 circuit boards, each with a surface area
measuring 2.0 in. \(\times 3.0\) in. The boards are covered with a
\(0.65-\mathrm{mm}\) layer of copper. In subsequent processing, \(85 \%\) of the
copper is removed. Copper has a density of \(8.96 \mathrm{~g} / \mathrm{cm}^{3}
.\) Calculate the masses of \(\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}
\mathrm{Cl}_{2}\) and \(\mathrm{NH}_{3}\)
needed to produce the circuit boards, assuming that the reaction used gives a
\(97 \%\) yield.
