Multiple choice 6- Upon the addition of 6M HCI to solution containing cations fr
ID: 558046 • Letter: M
Question
Multiple choice 6- Upon the addition of 6M HCI to solution containing cations from group I, Group II, A- Ag', Pb' and Group III a white precipitate forms, what cations could be present? (5 points) B-Cu2+, Bi3+ C-Fe2+, Np- 7- You took the supernatant from the previous question and added 6M HCI to make the pH 0.5 and then added 10 drops of 1M thioacetamide and black brownish precipitate forms, what cations could be present? (5 points) A- Ag', Pb2 8- You took the supernatant from question 7 and added enough 6M NHs until the solution is alkaline to litmus paper. After it was alkaline to litmus paper you added IM thioacetamide, heated the solution and centrifuged and a precipitate formed. What cations could be present? (5 points) A- Ag+, Pb2+ B- Cu2, Cd2 C Fe2, Ni2Explanation / Answer
Ans. #6. Correct option. A. Ag+ , Pb2+
The chlorides of Ag+, Pb2+ and Hg2+ cations are insoluble and form white precipitate with dilute HCl.
#7. Correct option – B. Cu2+ , Bi3+
Pb2+, Bi3+ and Cu2+ cations form black, brown precipitate with thioacetamide under acidic conditions (pH below, 3.0)-
2 Bi2+(aq) + 3 H2S(g, from thioacetamide) ----H+------> Bi2S3(s) + 6 H+ - brown ppt.
Cu2+(aq) + H2S(g, from thioacetamide) -----H+-----> CuS(s) + 2 H+ - Black ppt.
Note: Pb2+, being group II cation, has already been removed as white precipitate (PbCl2) in previous step.
#8. Correct options. C. Fe2+ , Ni2+
Fe2+and Ni2+ form black precipitate with thioacetamide under alkaline/ basic conditions -
Fe2+ + H2S(g, from thioacetamide) ---OH-----> FeS(s) + 2 H+ - Black ppt.
Ni2+ + H2S(g, from thioacetamide) ---OH-----> NiS(s) + 2 H+ - Black ppt.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.