conc. HNO3 + Cu

The solution of copper(II) ions in water is blue, but the solution of copper(II) ions in concentrated nitric acid is green.

Consider that copper metal is added to concentrated nitric acid.

Firstly, copper(II) ions are formed and most of the nitric acid is unreacted. Therefore, the solution is copper(II) ions in concentrated nitric acid, so that the colour is green.

After some time, most of the nitric acid has been reacted, and thus the blue colour of aqueous solution of copper(II) ions appears.
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002 的答案其實是把 001 答案用翻譯機翻譯，所以有些句子翻譯得一塌糊塗。

該解決方案的銅離子的水是藍色的，但解決銅離子的濃硝酸是綠色。

認為銅金屬添加到濃硝酸。

首先，銅離子的形成，大多數是未硝酸。因此，解決辦法是銅離子的濃硝酸，這樣的顏色是綠色。

一段時間後，大部分已被硝酸反應，因此，藍色的水溶液中銅離子的出現。