Devise a procedure that would confirm the presence of Pb^2+ ion in a mixture Pb^2+ and Cu^2+ ions. Devise a procedure that would confirm the presence of Ni^2+ ion in a mixture containing Pb^2+ and Ni^2+ ions. Based on the data explain why it would or would not be possible to confirm the presence of Cu^2+ and Ni^2+ ions in a mixture of the two.