Use the solubility rules from the Lab 4 introduction and your knowledge of qualitative separation schemes from the lab to answer
the following questions.
The qualitative analysis experiment you did is actually an abbreviated version of a much larger analysis scheme in which many different cations are separated and identified. Suppose a mixture contains Ag+, K+, NH4+, Hg22+, Pb2+, Mg2+, Sr2+, Ba2+, Cu2+, Al3+ and Fe3+.
(a) Which of the following ions could you separate, by causing them to precipitate, with the addition of HCl? (Hint: HCl is a source of chloride ions. Select all that apply.)
Ag+ K+ NH4+
Hg22+ Pb2+ Mg2+
Sr2+ Ba2+ Cu2+
Al3+ Fe3+
(b) After the addition of HCl, the above sample is centrifuged and decanted. Which of the following cations remaining in the supernatant could you separate, by causing them to precipitate, with the addition of H2SO4? (Hint: H2SO4 is a source of sulfate ions. Select all that apply.)
Ag+ K+ NH4+
Hg22+ Pb2+ Mg2+
Sr2+ Ba2+ Cu2+
Al3+ Fe3+
(c) After the addition of H2SO4, the above sample is centrifuged and decanted. Which of the following cations remaining in the supernatant could you separate, by causing them to precipitate, with the addition of H2CO3? (Hint: H2CO3 is a source of HCO3− and carbonate ions. Select all that apply.)
Ag+ K+ NH4+
Hg22+ Pb2+ Mg2+
Sr2+ Ba2+ Cu2+
Al3+ Fe3+
(d) Choose one of the cations above and write the net precipitation reaction that occurs. (Use the lowest possible coefficients. Include states-of-matter under the given conditions in your answer.)
Cu2+(aq) + (CO3)2-(aq) → CuCO3(s)
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