Question

Why does brass react with dilute hydrochloric acid and is corroded in rainy season to form CuCO3. Cu(OH)2?

Answer 1

Here is your answer-

Brass(Cu3Zn2) when reacts with Hydrochloric acid(diluted).
i.e Zn + 2HCl --------> ZnCl2+H2.
(Note that Copper in Brass will not react with HCl).

When Zinc chloride is exposed in rainwater in rainy season.
Then Zinc chloride react with water to dissociate itself in Zinc and chloride separately.
ZnCl2+H2O-----> Zn + Cl2.
After rains, it in Zinc in moist form react with oxygen,and gets corroded and forms ZnO(Zinc oxide).
i.e 2Zn+ O2 -------> 2ZnO.

Hope you understood.