Which gas is usually liberated when an acid reacts with a metal? | Unit2 Chemistry NCERT solution-Grade-10

Q.:-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:-

Usually, hydrogen gas is liberated when an acid reacts with a metal. For example, let us take the reaction between zinc and sulphuric acid, as per the apparatus set-up shown in the adjacent figure.

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A few pieces of zinc granules are taken in a test tube and about 5 mL of dilute H2SO4 is added. The gas produced is passed into a soap solution. We find that bubbles of soap solutions are formed. When a burning candle is brought near the soap bubbles, it burns with a pop sound which confirms the presence of hydrogen gas. 
Zinc granules react with dilute sulphuric acid to for zinc sulphate and hydrogen gas according to the chemical; equation:
Zn + H2SO4 —> ZnSO4 + H2