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

total volume of copper being rmoved is .215 *10^-3 * 8.75 * 10^-2 * 11.5 * 10^-2 *.735 *1100 = 1.75 * 10^-3 m^3

mass of copper being rmoved = 1.75* 10^-3 * 8.96 = .0157 grams .

moles of copper = .0157/molecular weight of copper =.0157 / 63.5 = 2.47*10^-4 moles

one mole of copper needs one mole of Cu(NH3)4Cl2.. so we need 2.47*10^-4 moles of Cu(NH3)4Cl2 .\

for this we need a mass of Cu(NH3)4Cl2 = moles * molar mass = 2.47*10^-4 * 202.575 = .05 grams

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