Kinetic studies of the formation of copper(I) in water + acetonitrile mixtures at 25 °C from the reversible reaction Cu2++ Cu0⇌ 2Cu+

Abstract

The rate of the forward reaction of the reversible reaction Cu2++ Cu0⇌2Cu+ has been measured at 25 °C in 150 cm3 of water + acetonitrile (H2O + AN) mixtures containing 5, 10, 20 and 40%(v/v) acetonitrile (AN) together with 0.032, 0.064, 0.16 and 0.32 mol dm–3 copper sulphate, 0.070 mol dm–3 H2SO4 and 1, 4 and 8 g of copper crystals 2–30 µm in size. The rate of the reaction is strongly influenced by the concentrations of copper sulphate and AN and by the amount and particle size of the copper crystals. The rate of the reaction in an atmosphere of nitrogen is not affected by up to 0.47 mol dm–3 H2SO4.The reaction under investigation is reasonably fast and in most cases goes almost to completion in 3–5 h. By reversing the reaction, the backward reaction becomes faster than the forward reaction and pure copper powder starts separating out from the solution. The present investigation is thus very useful for developing a cheap and quick method for the recovery of copper from crude samples.