Correct Answer: Option A

Explanation

The chemical equation, 2X + 2HCl  → 2XCl  +  H\(_2\)  indicates that element X reacts with hydrochloric acid to form a chloride salt with the formula XCl. This product formula implies that X has a valency of +1 (forming the ?\(^+\) ion), as the chloride ion (Cl\(^−\)) has a valency of -1. 

Among the given options, only Potassium (K) is an alkali metal (Group 1) that forms a +1 ion. Magnesium, Calcium, and Barium are alkaline earth metals (Group 2) that form +2 ions, which would produce a salt with the formula XCl\(_2\).

:. The correct answer is K - option A

There is an explanation video available below.

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