Why is not possible to prepare copper II sulphate by reacting copper metal with dilute sulphuric acid?
In simple terms it is because copper is below hydrogen in the Reactivity Series and so will not displace hydrogen from an acid. Copper will react with hot, concentrated sulphuric acid. The concentrated (but not the dilute) acid is an oxidising agent and will oxidise copper to the copper(II) ion and is itself reduced to sulphur dioxide (this used to be the standard lab preparation of SO2). The easiest way to make CuSO4 is to add copper(II) carbonate to the warm, dilute acid until the carbonate is in excess (it’s insoluble so will form a suspension) then filter off the excess carbonate and allow the filtrate to crystallise.
