Cation Groups and Precipitation
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Cation Groups and Precipitation

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Questions and Answers

Which group of cations is characterized by having insoluble chlorides?

  • Group V
  • Group II
  • Group I (correct)
  • Group III

    • Which of the following cations forms a black precipitate when reacted with H2S?

  • Cu 2+ (correct)
  • Bi 3+
  • Hg2 2+
  • Cd 2+ (correct)

    • Which chemical reagent is used to adjust the H+ concentration to 0.3 M in this analysis?

  • Sodium sulfide
  • Hydrochloric acid (correct)
  • Thioacetamide
  • Acetic acid

    • What color precipitate is formed by the cation Cd 2+ when reacted with sulfide ions?

    <p>Yellow</p> Signup and view all the answers

    What is the result of the reaction between Ag+ and HCl?

    <p>Formation of AgCl with a white precipitate</p> Signup and view all the answers

    Which compound can form a precipitate in a reaction involving magnesium from the alkaline earth group?

    <p>(NH4)2CO3</p> Signup and view all the answers

    What is the primary characteristic of the cations from Group 1 in relation to precipitation?

    <p>They remain in solution</p> Signup and view all the answers

    Which reagent is used to precipitate Group 3 cations during the separation process?

    <p>(NH4)2S</p> Signup and view all the answers

    After the precipitation of Group 1 cations, what should be done to the solution before adding H2S?

    <p>Increase the concentration of H+ to 0.3 M</p> Signup and view all the answers

    What happens to the remaining cations after the addition of the precipitant for Group 4?

    <p>They remain in aqueous solution</p> Signup and view all the answers

    Which alkaline earth metal is not included in the solubility category of Group II?

    <p>Na+</p> Signup and view all the answers

    Which step involves the use of sodium sulfide in the cation separation process?

    <p>Precipitation of Group 2</p> Signup and view all the answers

    Which of the following ions cannot form a precipitate with the common reagent NaOH?

    <p>NH4+</p> Signup and view all the answers

    What is the expected color of the precipitate when Sn 2+ is reacted with Na2S?

    <p>Brown</p> Signup and view all the answers

    Which sulfide is colored red and typically indicates the presence of mercuric ions?

    <p>HgS</p> Signup and view all the answers

    What is the color of the precipitate formed from Sb 3+/5+ when reacted with sulfur compounds?

    <p>Orange-red</p> Signup and view all the answers

    Which reagent is used for the precipitation of Fe 2+/3+ ions to form FeS or Fe2S3?

    <p>(NH4)2S</p> Signup and view all the answers

    Which of the following compounds represents the yellow precipitate formed from Sn 4+ ions?

    <p>SnS2</p> Signup and view all the answers

    In a flame test, which compound is indicative of the presence of sodium ions?

    <p>Yellow flame</p> Signup and view all the answers

    What is the result of mixing Cu with hydrogen sulfide?

    <p>CuS precipitate</p> Signup and view all the answers

    What ion characterization is typically identified by the black precipitate?

    <p>Fe 2+/3+</p> Signup and view all the answers

    Study Notes

    Cation Groups and Precipitation

    • Group I: Cations that are insoluble in water and precipitate as chlorides.
      • Members: Lead (Pb²⁺), Mercurous ion (Hg₂²⁺), and Silver (Ag⁺)
      • Precipitant: 3M HCl (Hydrochloric acid)
    • Group II: Cations that are insoluble in water and precipitate as sulfides, classified into subgroups.
      • Subgroup: Copper (Cu²⁺), Bismuth (Bi³⁺), Cadmium (Cd²⁺), Lead (Pb²⁺)
      • Precipitant: H₂S (Hydrogen sulfide)
      • Subgroup: Tin (Sn²⁺ / Sn⁴⁺), Arsenic (As³⁺ / As⁵⁺), Antimony (Sb³⁺ / Sb⁵⁺), Mercury (Hg²⁺)
      • Precipitant: Na₂S (Sodium sulfide)
    • Group III: Cations that precipitate as sulfides in basic solution.
      • Members: Iron (Fe²⁺ / Fe³⁺), Cobalt (Co²⁺), Nickel (Ni²⁺) and Manganese (Mn²⁺)
      • Precipitant: (NH₄)₂S (Ammonium sulfide)
    • Group IV: Cations that precipitate as carbonates in basic solution.
      • Members: Magnesium (Mg²⁺), Calcium (Ca²⁺), Strontium (Sr²⁺), Barium (Ba²⁺)
      • Precipitant: (NH₄)₂CO₃ (Ammonium carbonate)
    • Group V: Cations that remain in solution.
      • Members: Lithium (Li⁺), Sodium (Na⁺), Potassium (K⁺), Ammonium (NH₄⁺)
      • Precipitant: None

    Additional Key Points

    • Insoluble Cations: NH₄Cl, NH₃, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, CaCO₃, SrCO₃, BaCO₃
    • Solubilizing agents for Group II and III: Na₂S (Sodium sulfide), NaOH (Sodium hydroxide) and Na₂O₂ (Sodium Peroxide)
    • Experiment #3 Overview: Cations are precipitated in groups by using specific precipitating agents, separating them from the solution.
    • Precipitant: The substance used to cause the formation of a solid during the precipitation process.
    • Centrifugate: The liquid that remains after centrifugation, containing the remaining cations that were not precipitated.

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    Related Documents

    Table Guide - Group I-V Cations PDF

    Description

    Explore the fascinating world of cation groups and their precipitation reactions with various reagents. This quiz will cover the classification of cations into different groups based on solubility and the conditions under which they precipitate. Test your knowledge on the members of each group and the appropriate precipitants.

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