1) In a reaction when an element with displaces another element from its compound reaction.
2) Generally metals which are more active than hydrogen.
3) So, metal displaces the hydrogen from acids.
Example :
1) Take a small quantity of zinc dust in a conical flask.
2) Add dilute hydrochloric acid slowly.
3) Now take a balloon and tie it to the mouth of the conical flask.
4) Observation : We can observe that the gas bubbles coming out from the solution and the balloon bulges out.
5) Conclusion : Zinc pieces react with dil. `HCl` acid and liberate hydrogen gas.
6) Type of reaction : This is a chemical displacement reaction.
7) Chemical equation : `Zn_((s))+2HCl_((aq))rarrZnCl_(2(aq))+H_(2(g))uarr`.
