Qualitative Analysis of Group II Ions
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Questions and Answers

What is the concentration of each ion present in the unknown solution?

  • 0.1 mole per liter
  • 0.01 mole per liter
  • 0.05 mole per liter
  • 0.02 mole per liter (correct)

    • How much of the unknown solution is used for analysis?

  • 2 mL
  • 5 mL
  • 3 mL (correct)
  • 4 mL

    • What is added to the solution to make it acidic if it is alkaline?

  • 6 M HCl (correct)
  • 0.1 M KI
  • 1 M K2CrO4
  • 6 M NaOH

    • What indicates the presence of Ag+ and/or Hg22+ ions?

    <p>Formation of a curdy precipitate</p> Signup and view all the answers

    Why is the unused portion of the solution reserved?

    <p>Against the possibility of loss of the first sample during absence of certain ions</p> Signup and view all the answers

    What is the purpose of adding 6 M HCl to the solution?

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

    What is the purpose of adding 2 drops of 6 M HCl to the filtrate?

    <p>To ensure completeness of precipitation</p> Signup and view all the answers

    What is the purpose of heating the water to boiling?

    <p>To facilitate the transfer of the precipitate</p> Signup and view all the answers

    What is the purpose of adding 1 M K2CrO4 to the filtrate?

    <p>To form a yellow precipitate of PbCrO4</p> Signup and view all the answers

    What should be done if the filtrate appears cloudy after initial filtration?

    <p>Repeat the filtration process until the filtrate is clear</p> Signup and view all the answers

    What is the purpose of washing the filter with 1 M HCl?

    <p>To remove any impurities from the filter</p> Signup and view all the answers

    What is the final step in confirming the presence of Pb2+ ions?

    <p>Re-forming the yellow precipitate with 6 M acetic acid</p> Signup and view all the answers

    Study Notes

    Ion Concentration and Analysis

    • Concentration of each ion in the unknown solution must be determined through analytical methods.
    • A specific volume of the unknown solution is used for accurate analysis, typically a small aliquot.

    Adjusting Solution pH

    • To make an alkaline solution acidic, a strong acid, often 6 M HCl, is added.

    Ion Detection

    • The presence of ions such as Ag+ and/or Hg22+ can be indicated by specific color changes or precipitate formation during reactions.

    Sample Preservation

    • The unused portion of the solution is reserved for potential further analysis or confirmatory tests.

    6 M HCl Addition

    • Adding 6 M HCl helps to precipitate certain ions by lowering the pH and ensuring solubility conditions are met for specific reactions.

    Filtrate Treatment

    • Two drops of 6 M HCl are added to the filtrate to check for the presence of any remaining ions that could precipitate under acidic conditions.

    Heating Steps

    • Heating the water to boiling serves to dissolve compounds fully and facilitate reactions that might be temperature-dependent.

    Adding K2CrO4

    • 1 M K2CrO4 is added to the filtrate as it reacts with specific cations, forming a colored precipitate indicative of certain metal ions like Pb2+.

    Managing Filtrate Clarity

    • If the filtrate appears cloudy after initial filtration, it must be filtered again to remove undissolved particles.

    Filter Washing

    • Washing the filter with 1 M HCl ensures that any residual ions on the filter are removed, providing a cleaner sample for analysis.

    Confirming Pb2+ Presence

    • The final step to confirm Pb2+ involves the detection of a characteristic yellow precipitate when K2CrO4 is added, confirming the presence of lead ions.

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    Quiz Team

    Description

    This quiz is about identifying ions present in a given unknown using various reagents and materials. It involves the analysis of Group II ions, including Ag+, Pb2+, and Hg22+.

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