Which of the following reactions represents and acid-base reaction according to Lewis theory but not according to Bronsted-Lowry theory?
a) NH3 + HCl --> NH4Cl
b) 2H2O <--> H3O+ + OH-
c) Cu2+ + 4NH3 <--> [Cu(NH3)4]2+
d) BaO + H2O <--> Ba2+ + 2OH-
Answer: c) Cu2+ + 4NH3 <--> [Cu(NH3)4]2+
as there is no exchange of H+