When Zn dust is added to sufficiently large volume of aqueous solution of copper sulphate. 3.175 g of copper metal and 20 J of heat is evolved. The ΔH for the reaction is:
Zn(s)+CuSO4(aq)⟶ZnSO4(aq)+Cu(s)
(Atomic weight of Zn=65.3, atomic weight of Cu=63.5)