Qualitative Analysis of Anions
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Questions and Answers

What is the main purpose of a reagent in qualitative analysis?

  • To react selectively with one of the ions to produce a change (correct)
  • To represent a chemical reaction as a net ionic equation
  • To remove the carbonate and phosphate ions from the solution
  • To identify the unknown substance

    • What is the difference between a positive test and a negative test?

  • A positive test is used to identify the type of ion, while a negative test is used to determine its concentration
  • A positive test is used to remove impurities, while a negative test is used to add impurities
  • A positive test indicates the presence of an ion, while a negative test indicates its absence (correct)
  • A positive test is used to test for anions, while a negative test is used to test for cations

    • What is the purpose of acidifying the solution in the anion tests?

  • To increase the concentration of the anions
  • To produce a gas
  • To remove the carbonate and phosphate ions that may affect the observation of other ions (correct)
  • To change the color of the solution

    • What is the result of the chloride ion test?

    <p>A white precipitate</p> Signup and view all the answers

    How many anion tests are performed in the experiment?

    <p>5</p> Signup and view all the answers

    What is the term for the change that occurs when a chemical reaction takes place?

    <p>Formation or disappearance of a characteristic</p> Signup and view all the answers

    What is the result of the reaction between AgNO3 and NaCl?

    <p>A white precipitate of AgCl is formed</p> Signup and view all the answers

    What is the purpose of adding 6M HCl to the solution in the sulfate ion test?

    <p>To acidify the solution</p> Signup and view all the answers

    Which reagent is used to test for the presence of nitrate ions?

    <p>FeSO4</p> Signup and view all the answers

    What is the observation when carbonate ions are present in the solution?

    <p>A gas is evolved</p> Signup and view all the answers

    What is the purpose of heating the solution in the phosphate ion test?

    <p>To promote the formation of a yellow precipitate</p> Signup and view all the answers

    What is the formula of the compound formed when BaCl2 reacts with Na2SO4?

    <p>BaSO4</p> Signup and view all the answers

    Study Notes

    Objectives

    • Learn to identify anions from their typical chemical reactions
    • Learn to represent a chemical reaction as a net ionic equation

    Changes in Chemical Reactions

    • Formation or disappearance of:
      • Colour
      • Solid (precipitate)
      • Gas
      • Light
      • Heat
      • Change in instrument readings

    Qualitative Analysis

    • Reagent: a chemical substance that reacts selectively with one ion in the unknown to produce a change
    • Two types of tests:
      • Positive test: substance (anion or cation) is present in the unknown
      • Negative test: substance (anion or cation) is absent or present in low concentration

    Anion Tests

    • Five anion tests:
      • Chloride ion test (Cl-)
      • Sulfate ion test (SO42-)
      • Nitrate ion test (NO3-)
      • Carbonate ion test (CO32-)
      • Phosphate ion test (PO43-)

    Anion Tests Reactions

    • Chloride ion test: AgNO3 + NaCl → AgCl (white ppt) + NaNO3 (acidified with 6M HNO3)
    • Sulfate ion test: BaCl2 + Na2SO4 → BaSO4 (white ppt) + 2NaCl (acidified with 6M HCl)
    • Nitrate ion test: 8FeSO4 + 2NaNO3 + 4H2SO4 → [FeNO]SO4 (brown ring) + 3Fe2(SO4)3 + Na2SO4 + 4H2O (acidified with 6M H2SO4)
    • Carbonate ion test: Na2CO3 + 2HCl → 2NaCl + H2O + CO2 (gas) (using 6M HCl)
    • Phosphate ion test: Na3PO4 + 12(NH4)2MoO4 + 24HNO3 → (NH4)3[PO4(MoO3)12] (yellow ppt) + 3NaNO3 + 21NH4NO3 + 12H2O (heated using water bath)

    Net Ionic Equation

    • Chloride ion test: Ag+ + Cl- → AgCl (ppt)
    • Formula: Molecular equation → Total ionic equation → Net ionic equation

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    Quiz Team

    Description

    This quiz covers the identification of anions from their chemical reactions and representation of chemical reactions as net ionic equations. It also includes changes observed in chemical reactions, such as formation or disappearance of color, solid, gas, light, heat, and changes in instrument readings. Learn how to analyze anions using reagents and chemical reactions.

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