G is a colourless crystalline solid which reacts with dilute nitric acid to give a colourless solution, H, and a colourless, odourless has, I, which turns limewater milky. G has a lilac flame colour. State the names of G, H and I?

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Mevin Wan Wan

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Hi Addie. I hope you are well. Since the 'gas I' can turn the limewater milky, it must be carbon dioxide gas, meaning the crystalline solid is a carbonate salt. Here, we know that reaction between nitric acid and carbonate salt will form metal nitrates, water and carbon dioxide gas. Moreover, the question also mentioned that G has a lilac flame colour when burned, meaning this species contains potassium. Intuitively, we come to the conclusion that the colourless solid G is potassium carbonate (K_2CO_3). The colourless solution H is potassium nitrate solution. Below shows the chemical equation for the reaction above: HNO_3 + K_2CO_3 -> KNO_3 + CO_2 + H_2O