NaCl is a salt of strong acid (HCl) and a strong base (NaOH).Therefore, its solution is neutral with
pH = 7
CuSO4 is a salt of strong acid (H2SO4) and weak base [CU(OH)2]. Therefore, its solution is acidic with pH <7.
Na2CO3 is a salt of strong base (NaOH) and weak acid (H2CO3). Therefore, its solution is basic with pH >7.