To Identify The Acid Radical Present In A Given Sample Of Salt (s3). | Grade Xi

APPARATUS REQUIRED

• Test tubes
• Test tube rack
• Bunsen burner
• Wire gauze
• Tripod stand
• Forceps
• Litmus paper
• Spatula
• Graduated cylinder
• Dropper

CHEMICAL REQUIRED

• Dilute hydrochloric acid (HCl)
• Dilute sulfuric acid (H2SO4)
• Dilute nitric acid (HNO3)
• Sodium hydroxide (NaOH)
• Barium chloride (BaCl2)
• Silver nitrate (AgNO3)
• Lead acetate (Pb(CH3COO)2)
• Potassium dichromate (K2Cr2O7)
• Phenolphthalein indicator

THEORY

The acid radical present in a salt can be identified by observing the following:

• The reaction of the salt with dilute acids: If the salt reacts with a dilute acid to produce an acidic solution, then the anion of the salt is a weak base. If the salt reacts with a dilute acid to produce a neutral solution, then the anion of the salt is a strong base.
• The reaction of the salt with sodium hydroxide: If the salt reacts with sodium hydroxide to produce a basic solution, then the anion of the salt is a weak acid. If the salt reacts with sodium hydroxide to produce a neutral solution, then the anion of the salt is a strong acid.
• The reaction of the salt with barium chloride: If the salt reacts with barium chloride to produce a white precipitate, then the anion of the salt is a sulfate ion.
• The reaction of the salt with silver nitrate: If the salt reacts with silver nitrate to produce a white precipitate, then the anion of the salt is a chloride ion.
• The reaction of the salt with lead acetate: If the salt reacts with lead acetate to produce a yellow precipitate, then the anion of the salt is a chromate ion.
• The reaction of the salt with potassium dichromate: If the salt reacts with potassium dichromate to produce a green precipitate, then the anion of the salt is a bromide ion.

PROCESS

1. Take a small amount of the salt in a test tube.
2. Add a few drops of dilute hydrochloric acid to the test tube.
3. Observe the reaction between the salt and the acid.
4. If the reaction produces an acidic solution, then the anion of the salt is a weak base. If the reaction produces a neutral solution, then the anion of the salt is a strong base.
5. Add a few drops of sodium hydroxide to the test tube.
6. Observe the reaction between the salt and the sodium hydroxide.
7. If the reaction produces a basic solution, then the anion of the salt is a weak acid. If the reaction produces a neutral solution, then the anion of the salt is a strong acid.
8. Add a few drops of barium chloride to the test tube.
9. Observe the reaction between the salt and the barium chloride.
10. If the reaction produces a white precipitate, then the anion of the salt is a sulfate ion.
11. Add a few drops of silver nitrate to the test tube.
12. Observe the reaction between the salt and the silver nitrate.
13. If the reaction produces a white precipitate, then the anion of the salt is a chloride ion.
14. Add a few drops of lead acetate to the test tube.
15. Observe the reaction between the salt and the lead acetate.
16. If the reaction produces a yellow precipitate, then the anion of the salt is a chromate ion.
17. Add a few drops of potassium dichromate to the test tube.
18. Observe the reaction between the salt and the potassium dichromate.
19. If the reaction produces a green precipitate, then the anion of the salt is a bromide ion.

OBSERVATIONS

The observations made during the experiment are as follows:

• The reaction of the salt with dilute hydrochloric acid produced an acidic solution.
• The reaction of the salt with sodium hydroxide produced a basic solution.
• The reaction of the salt with barium chloride produced a white precipitate.
• The reaction of the salt with silver nitrate produced a white precipitate.
• The reaction of the salt with lead acetate produced a yellow precipitate.
• The reaction of the salt with potassium dichromate produced a green precipitate.

OBSERVATION TABLE

Test	Observation
Reaction with dilute hydrochloric acid	Acidic solution
Reaction with sodium hydroxide	Basic solution
Reaction with barium chloride	White precipitate
Reaction with silver nitrate	White precipitate
Reaction with lead acetate	Yellow precipitate
Reaction with potassium dichromate	Green precipitate

Calculation

The calculation of the formula of the salt is as follows:

• The anion of the salt is a sulfate ion.
• The cation of the salt is a barium ion.
• The formula of the salt is BaSO4.

RESULTS

The results of the experiment are as follows:

• The acid radical present in the given sample of salt is a sulfate ion.
• The formula of the salt is BaSO4.

PRECAUTIONS

• Handle all chemicals with care.
• Wear a lab coat, safety goggles, and gloves when performing the experiment.
• Do not heat the test tubes directly over the Bunsen burner.
• Keep the test tubes away from the Bunsen burner when they are not being heated.
• Do not dispose of chemicals in the sink.