Answer:
Compound X would be an acid whose pH is below 7 and is able to react with calcium carbonate, a slightly basic salt.
Explanation:
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In this case, according to the given information, it turns out possible for us to firstly say that the calcium carbonate is a slightly basic salt, which is likely to react with acids and produce effervescence due to the release of carbon dioxide gas. Moreover, since the compound X exhibited a pH below 7 when dissolved in water, it is 100% sure that this compound is an acid, due to these two reasonings.
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