Question

what gas is liberated when HCl is reacted with active metal

Answer 1

HYDROGEN GAS IS LIBERATED

Answer 2

The reduction potential of active metals like Na, K is negative while that of hydrogen is zero. So, hydrogen will easily get reduced (actually the H+ ions will get reduced to form H2) and in turn will oxidise these metals, causing them to lose their electrons. In this case the active metal ion will bind to the chloride in the solution and NaCl or KCl will be formed depending on the active metal you take.

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