Question

what happen when we dip copper coin in nitric solution????

Answer 1

A few drops of nitric acid are placed on an older copper penny (and the reaction is shown). ... The reaction produces red-brown nitrogen dioxide gas and a hot, concentrated solution of copper(II) nitrate, which is blue. As the water evaporates and the solution cools, crystals of Cu(NO3)2(s) begin to form.

Answer 2

In simple words it forms a red-brown nitrogen dioxide.