Why Is Basic Copper Carbonate Blue Instead Of Green?

Update:16-08-2019
Summary:

A high concentration of carbonate ions may also form so […]

A high concentration of carbonate ions may also form soluble complex ions with Cu2+. A small amount of copper sulfate solution is added dropwise to a larger amount (usually more than 20ml) of saturated Basic Copper Carbonate (WSDTY) solution, and stirred, the precipitate will be redissolved to obtain bright blue or even The indigo solution is believed to be a soluble [Cu(CO3)2]2- complexion. It is also mentioned in the literature that after mixing a concentrated CuSO4 solution with an excess of concentrated K2CO3 solution, in addition to the precipitation of basic copper carbonate xCuCO3·yCu(OH)2, K2[Cu(CO3)2] crystals may be precipitated. It is also possible to use sodium bicarbonate solution instead of a sodium carbonate solution, so that it is easy to obtain a precipitate having a composition close to that of Cu2(OH)2CO3, but the reaction is more intense, and a large amount of CO2 bubbles or even foam is generated, and the feed rate must be controlled to prevent the reaction from being uncontrolled. material.

If the preparation of copper hydroxide precipitate is reversed, the method of adding copper sulfate solution to sodium hydroxide solution should be adopted, and the pH of the solution should be controlled to be high, so that blue Cu(OH)2 precipitate can be obtained. If it is reversed, there is a high concentration of SO4 2- in the solution, which is easy to precipitate blue-green basic copper sulfate xCuSO4·yCu(OH)2 precipitate. Some data describe the chemical formula of this basic copper sulfate precipitation as Cu2 (OH). ) 2SO4.

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