Separate /save some unknown
• DR ROB’S “Get to the point of this lab!”
• Worksheet
• Postive cations like Pb2+ , Ag + and ...
Pb2+ Cr2O72-
.
• The most confusing ion is the S2- ion
• In acidic and in basic solutiopn
• Chemlab sheet
• Centiguge sheet
Best website
• http://www.dartmouth.edu/~chemlab/chem3
-5/qual_cat/full_text/procedure.html
.
• FROM BOOK RIGHT TO ADEMDUM
• MENTION 12 IONS
• YOU WILL DO THREE TODAY
• DO ADDEMDUM FIRST
• THEN GO TO BOOK
• REVIEW ...
.
• EASY FOR SOMETHING TO OCCUR DURING
THESE LABS
• MUST PLAN BEFORE YOU GET HERE
• USE OR LAB BOOK TO WRITE DOWN
REACTION...
.
#1 – Qualitative Analysis
• Principles of Qualitative Analysis
1.Confirmatory Tests:
These are tests that determine conc...
.
Separations:
These are procedures that separate groups of
ions from other groups, or individual ions in a
mixture of ion...
Precipitation and Separation of Group
I Cations:
• Group 1: The silver group: Ag+, Hg22+,
Pb2+ -----These ions precipitate...
You know some of this already
• You have already done lead in CHM121
• And,
• You have just done another ion similar to Ni...
Just add hot water
These cations are Pb+2, Hg2
• +2, and Ag+ are all insoluble in cold water.
Precipitation and Separation of Group
I Cations:
• Precipitation and Separation of Group I
Cations:
• Pb+2, Hg2+2, and Ag+...
chloro-complexes may form !!
• It is important to add enough HCl to ensure
complete precipitation, but not too large an
ex...
Precipitation and Separation of Group
I Cations:
• Lead chloride can be separated from AgCl
and Hg2Cl2 by heating with wat...
Begin . . . . . .
• Show the PDF
• Show the word files
• Show flow chart now
Precipitation and Separation of Group
I Cations:
• Hg2Cl2 can be distinguished from AgCl by
reaction with ammonia via oxid...
.
• Hg2Cl2(white solid) + 2 NH3(aq)
→
• NH4+(aq) + Cl-(aq) + Hg(black
liquid) + HgNH2Cl(white solid)
Hg2Cl2(white solid) + 2 NH3(aq) →
NH4+(aq) + Cl-(aq) + Hg(black liquid) +
HgNH2Cl(white solid)
Aminomercuric chloride
and,
• Silver chloride also reacts with aqueous
ammonia to form a complex ion that remains
in solution. Addition of a
• strong ...
• Silver chloride also reacts with aqueous ammonia to form a complex ion that remains in
solution. Addition of a
• strong ...
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Presentation1qualonefirsdttryyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy carpenter sy

  1. 1. Separate /save some unknown • DR ROB’S “Get to the point of this lab!” • Worksheet • Postive cations like Pb2+ , Ag + and Hg+ • Can be ptt by OH-, Cr2O72-, S2- • And Cl-
  2. 2. Pb2+ Cr2O72-
  3. 3. . • The most confusing ion is the S2- ion • In acidic and in basic solutiopn • Chemlab sheet • Centiguge sheet
  4. 4. Best website • http://www.dartmouth.edu/~chemlab/chem3 -5/qual_cat/full_text/procedure.html
  5. 5. . • FROM BOOK RIGHT TO ADEMDUM • MENTION 12 IONS • YOU WILL DO THREE TODAY • DO ADDEMDUM FIRST • THEN GO TO BOOK • REVIEW CENTRIFUGE
  6. 6. . • EASY FOR SOMETHING TO OCCUR DURING THESE LABS • MUST PLAN BEFORE YOU GET HERE • USE OR LAB BOOK TO WRITE DOWN REACTIONS-MANY TESTSTUBES ALL AT ONCE!
  7. 7. . #1 – Qualitative Analysis • Principles of Qualitative Analysis 1.Confirmatory Tests: These are tests that determine conclusively that a certain ion is present. Interfering ions are removed before a confirmatory test is done. • .
  8. 8. . Separations: These are procedures that separate groups of ions from other groups, or individual ions in a mixture of ions. Separations are followed by confirmatory tests to identify the separated ion.
  9. 9. Precipitation and Separation of Group I Cations: • Group 1: The silver group: Ag+, Hg22+, Pb2+ -----These ions precipitate (as the chlorides) from 0.3M HCl solution. • « » »Rationale: Softest acids>>>>>>>> • react strongly enough with a borderline base • to precipitate in acid solution..
  10. 10. You know some of this already • You have already done lead in CHM121 • And, • You have just done another ion similar to Ni– which will get to shorty (Cu(NH3)4)
  11. 11. Just add hot water These cations are Pb+2, Hg2 • +2, and Ag+ are all insoluble in cold water.
  12. 12. Precipitation and Separation of Group I Cations: • Precipitation and Separation of Group I Cations: • Pb+2, Hg2+2, and Ag+ are all insoluble in cold water. • They can be removed as a group from solution by the addition of HCl via simple precipitation: Ag+ + Cl- → AgCl(s)
  13. 13. chloro-complexes may form !! • It is important to add enough HCl to ensure complete precipitation, but not too large an excess. In highly concentrated HCl solutions, chloro-complexes may form such as • AgCl2-1.
  14. 14. Precipitation and Separation of Group I Cations: • Lead chloride can be separated from AgCl and Hg2Cl2 by heating with water, essentially reversing the above reaction. • Once Pb+2 is in solution, you can discern its presence by adding chromate ion to produce a yellow solid: • Pb+2 + CrO4-2 → PbCrO4(s) (yellow)
  15. 15. Begin . . . . . . • Show the PDF • Show the word files • Show flow chart now
  16. 16. Precipitation and Separation of Group I Cations: • Hg2Cl2 can be distinguished from AgCl by reaction with ammonia via oxidation reduction to yield finely divided black metallic mercury and a white complex compound HgNH2Cl. As the reaction proceeds, the solid appears to change colors from white to black or gray:
  17. 17. . • Hg2Cl2(white solid) + 2 NH3(aq) → • NH4+(aq) + Cl-(aq) + Hg(black liquid) + HgNH2Cl(white solid)
  18. 18. Hg2Cl2(white solid) + 2 NH3(aq) → NH4+(aq) + Cl-(aq) + Hg(black liquid) + HgNH2Cl(white solid)
  19. 19. Aminomercuric chloride and,
  20. 20. • Silver chloride also reacts with aqueous ammonia to form a complex ion that remains in solution. Addition of a • strong acid will destroy the complex and confirm the presence of silver ion by re- precipitating the white AgCl solid:
  21. 21. • Silver chloride also reacts with aqueous ammonia to form a complex ion that remains in solution. Addition of a • strong acid will destroy the complex and confirm the presence of silver ion by re-precipitatin the white AgCl solid: • AgCl(s) + 2 NH3(aq) → Ag(NH3)2 +(aq) + Cl-(aq) • Ag(NH3)2+(aq) + 2 H+(aq)+ Cl-(aq) → AgCl(s) + 2 NH4aq)

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