Question

which gas is usually liberated when an acid reacts with a metal? illustrate with an example. How will you test for the presence of this gas?

Answer 1

when an acid reacts with an active metal HYDROGEN gas is liberated.

EXCEPTION - acids does not react with element bellow hydrogen in activity series of metals to give hydrogen because such metals cannot displace hydrogen from the acid


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EXAMPLE -

Zn + H2SO4 ------> ZnSO4 + H2

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TEST -

1)Burning wooden splinter is extinguished in hydrogen

2)hydrogen burns with a pale blue flame producing pop sound.

Answer 2

when acid react with metal then hydrogen gas is librated by the reaction .
example :-
2HCl + 2Na → 2NaCl + H2( ↑)

testing of hydrogen gas :- H2 gas is highly cumbusible gas and burn in air or dioxygen with pale blue flame to form water and hear pop sound . hence if we librated gas contact with air then it combused with pale blue flame , hear pop sound and some amount of water form . then we can say that the gas is must be dihydrogen gas ( H2)
e.g H2(g) + O2(g) → H2O(l)