CBSE Class 10 Answered

Copper does not react with hydrochloric acid in the sense of single replacement because copper is lower on the activity series than hydrogen which is the active component of the acid. This is due to the change of an electron configuration of [Ar] 4s² 3d⁹ to [Ar] 4s¹ 3d¹⁰ when it comes in contact with reactive species. This half-filled subshells which are more stable makes copper less reactive. So copper will form complex if the concentrated HCl is used.