In the production of printed circuit boards for the electronics industry, a 0.21

Question

In the production of printed circuit boards for the electronics industry, a 0.215 mm layer of copper is laminated onto an insulating plastic board. Next a circuit pattern made of a chemically resistant polymer is printed on the board. The unwanted copper is removed by chemical etching and the protective polymer is finally removed by solvents. One etching reaction is

Cu(NH3)4Cl2(aq) + 4NH3(aq) + Cu(s) ? 2Cu(NH3)4Cl(aq)

A plant needs to manufacture 11000 printed circuit boards, each 8.75cm x 11.5cm in area. An average of 73.5% of the copper is removed from each board (density of copper=8.96g/cm3.) What mass of Cu(NH3)4Cl2 reagent is required?

Explanation / Answer

Cu(NH3)4Cl2(aq) + 4 NH3(aq) + Cu(s) => 2 Cu(NH3)4Cl(aq)

Total area = 11000 x 8.75 x 11.5 = 1106875 cm2

Thickness = 0.215 mm = 0.0215 cm

Volume of Cu = area x thickmess = 1106875 x 0.0215 = 23797.8 cm3


Mass of Cu = volume x density

= 23797.8 x 8.96 = 213228.4 g


Mass of Cu removed = 73.5/100 x 213228.4 = 156722.9 g

Moles of Cu(NH3)4Cl2 required = moles of Cu removed = mass/molar mass of Cu

= 156722.9/63.546 = 2466.29 mol


Mass of Cu(NH3)4Cl2 = moles x molar mass of Cu(NH3)4Cl2

= 2466.29 x 202.575

= 4.996 x 10^5 g = 5.00 x 10^5 g

= 499.6 kg = 500 kg

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