Question

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Answer 1

Amphoteric metals like zinc, aluminium reacts with both acids and bases to produce hydrogen gas.

Out of the following metals which will give H2 on reaction with NaOH : I : Zn II : Mg III : Al IV : Be (1) I, II, III, IV (2) I, III, IV (3) II, IV (4) I, III

Answer 2

Question :

Which of the following metals will give H₂ on reaction with NaOH ?

(a) Mg                    (b) Ba

(c) Ca                     (d) Sr              

Answer :

Mg

Explanation :    

Metals normally liberate hydrogen when they react with acids .

For example : Sodium reacts with Sulphuric acid to give hydrogen .

But here we are asked which metal will liberate hydrogen upon reacting with strong base .

The answer will be magnesium .

The reaction will be :

$\mathsf{Mg+2NaOH\rightarrow Na_2MgO_2+H_2\uparrow}$    

The metal zinc ( Zn ) will also react with NaOH liberating hydrogen .

Actually amphoteric metals react with both acids and bases liberating hydrogen .

Hence your answer is magnesium !