Lab Experiment: Sodium Removal
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Questions and Answers

What volume of filtrate is used in the nitrogen detection test?

  • 1 ml
  • 4 ml
  • 2 ml
  • 3 ml (correct)

    • How many drops of ferrous sulfate solution are added during the nitrogen detection test?

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

    • To make the solution basic, what percentage of NaOH solution is used?

  • 10% (correct)
  • 20%
  • 15%
  • 5%

    • For how long should the solution be heated to boil during the nitrogen detection test?

    <p>30 sec.</p> Signup and view all the answers

    What indicates a positive test for nitrogen?

    <p>Prussian blue precipitate</p> Signup and view all the answers

    What is the role of acetic acid in the detection of sulfur?

    <p>It acidifies the solution, allowing the formation of lead sulfide.</p> Signup and view all the answers

    Which compound forms a black precipitate indicating the presence of sulfur?

    <p>Lead sulfide</p> Signup and view all the answers

    If lead acetate is omitted from the experiment, what would be the observed result?

    <p>No black precipitate would form.</p> Signup and view all the answers

    Which product is NOT formed in the reaction involving sodium sulfide and lead acetate?

    <p>Acetic acid</p> Signup and view all the answers

    What is the chemical formula for lead sulfide?

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

    In the preparation of sodium ferrocyanide, what role does NaOH play in the reaction?

    <p>Basic medium for the reaction between NaCN and FeSO4</p> Signup and view all the answers

    Which compound is formed as an intermediate before sodium ferrocyanide during the preparation steps?

    <p>Iron(II) cyanide (Fe(CN)2)</p> Signup and view all the answers

    What is the overall charge of the ferric ferrocyanide complex Fe4[Fe(CN)6]3?

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

    Which of the following statements is incorrect regarding the structure of sodium ferrocyanide?

    <p>The complex includes four cyanide ions.</p> Signup and view all the answers

    During the preparation of ferric ferrocyanide, what is the by-product formed along with ferric ferrocyanide?

    <p>Na2SO4</p> Signup and view all the answers

    What is the primary purpose of adding alcohol to the test tube containing excess unreacted sodium before breaking it with heating?

    <p>To react with excess sodium to form sodium alkoxide</p> Signup and view all the answers

    Why should the test tube be cautiously dropped into a beaker containing 20ml of D.W.?

    <p>To prevent sudden breakage and splattering of contents</p> Signup and view all the answers

    What is the expected appearance of the filtrate after the solution is heated to boiling and filtered?

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

    Which chemical reaction correctly describes the formation of sodium alkoxide in the experiment?

    <p>2 Na + 2 CH_3CH_2OH → 2 NaOCH_2CH_3 + H_2</p> Signup and view all the answers

    What should be done if the test tube does not break down after being dropped into the solution?

    <p>Use a glass rod to break it</p> Signup and view all the answers

    Study Notes

    Steps for the Experiment

    • Cautiously drop the hot test tube into a beaker containing 20ml of distilled water to break it down.
    • Use a glass rod if the tube doesn't break down.
    • Heat the resulting solution to boiling and filter it.
    • The filtrate should be colorless and is used for specific tests.

    Removing Excess Sodium

    • Add a small quantity of alcohol to the test tube before breaking it with heating to react with excess sodium, producing sodium alkoxide.
    • The chemical equation for this reaction is 2Na + 2CH₃CH₂OH → 2NaOCH₂CH₃ + H₂.

    Detection of Nitrogen

    • Add 4 drops (0.2 gm) of ferrous sulfate solution to 3 ml of the filtrate.
    • Make the solution basic by adding enough NaOH solution (10%).
    • Heat the solution for 30 seconds and then make it acidic by adding drops of dilute H₂SO₄.
    • A Prussian blue precipitate indicates a positive test for nitrogen.

    Preparation of Ferrocyanides

    • Sodium cyanide (NaCN) is prepared by fusion of sodium, carbon, and nitrogen from an organic compound.
    • NaCN reacts with ferrous sulfate to form ferricyanide and sodium sulfate in the presence of basic NaOH.
    • Ferricyanide reacts with sodium cyanide to form sodium ferrocyanide.
    • Sodium ferrocyanide reacts with ferric sulfate to form ferric ferrocyanide, which has a blue color and is formed during boiling.

    Chemical Structure

    • The structure of ferric ferrocyanide is a square planar complex with a central iron atom bonded to four cyanide ions.
    • Each cyanide ion is bonded to the nitrogen atom of a neighboring cyanide ion.
    • The overall charge of the complex is -4, which is balanced by four sodium ions.

    Chemical Formula

    • The chemical formula for ferric ferrocyanide is [Fe(CN)₆]³⁻.
    • The chemical formula for sodium ferrocyanide is [Fe(CN)₆]⁴⁻.

    Detection of Sulfur

    • Acidify 2 ml of the filtrate with dilute acetic acid.
    • Add 5 drops of lead acetate solution to the acidified filtrate.
    • A black precipitate of lead sulfide indicates the presence of sulfur.
    • The chemical equation for this reaction is Na₂S + (CH₃COO)₂Pb → PbS + 2CH₃COONa.

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    Description

    This quiz is about a laboratory experiment involving the removal of excess sodium. It outlines the steps to follow, including the preparation of a solution and its subsequent filtering.

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