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%

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

30 sec. Signup and view all the answers

What indicates a positive test for nitrogen?

Prussian blue precipitate Signup and view all the answers

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

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

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

Lead sulfide Signup and view all the answers

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

No black precipitate would form. Signup and view all the answers

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

Acetic acid Signup and view all the answers

What is the chemical formula for lead sulfide?

PbS Signup and view all the answers

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

Basic medium for the reaction between NaCN and FeSO4 Signup and view all the answers

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

Iron(II) cyanide (Fe(CN)2) Signup and view all the answers

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

Neutral Signup and view all the answers

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

The complex includes four cyanide ions. Signup and view all the answers

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

Na2SO4 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?

To react with excess sodium to form sodium alkoxide Signup and view all the answers

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

To prevent sudden breakage and splattering of contents Signup and view all the answers

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

Colorless Signup and view all the answers

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

2 Na + 2 CH_3CH_2OH → 2 NaOCH_2CH_3 + H_2 Signup and view all the answers

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

Use a glass rod to break it 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.