When a copper wire is left in silver nitrate solution, it is observed that the solution turns bluish green. (a) Explain the observation. (b) Write the balanced chemical equation to represent the change taking place.

(a) Copper is higher than silver in the activity series of metals. It displaces silver from silver nitrate and forms copper nitrate which gives a bluish green colour in the solution.
(b) Cu(s) + 2AgNO₃ (aq) ⟶ Cu(NO₃)₂ (aq) + 2Ag (s)