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After creating a solution of copper(II)-sulfate-pentahydrate, water and concentrated ammonia, the newly formed complex (tetraamminecopper(II)-sulfate-monohydrate) is completely dissolved in water. By adding ethanol, one is able to decrease the solubility of that complex in water and have crystals percipitates out of solution.

Since the complex is not soluble in ethanol, I am having trouble understanding why adding ethanol changes anything about the solubility of the complex. Would adding some organic phase like petrol ether or a non-soluble solid such as ceramic pellets do the same?

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Would adding some organic phase like petrol ether or a non-soluble solid such as ceramic pellets do the same?

No. But adding other organic solvents which are miscible with water would.

The idea behind the "trick" is to reduce the polarity of the aqueous phase. With other words, you're making water more ethanol-like.

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