To Identify Basic Radicals Present In Given Salt Sample. | Grade Xi

APPARATUS REQUIRED

• Test tubes
• Test tube holder
• Bunsen burner
• Wire gauze
• Spatula
• Dropper
• pH paper or pH meter
• Safety goggles
• Gloves

CHEMICALS REQUIRED

• Solid salt sample
• Dilute hydrochloric acid (HCl)
• Dilute sodium hydroxide (NaOH)
• Phenolphthalein solution
• Methyl orange solution
• Litmus paper

THEORY

Basic radicals are ions that can accept protons (H+ ions) to form a base. They are typically metal ions, such as sodium (Na+), potassium (K+), and calcium (Ca2+). When a salt containing a basic radical is dissolved in water, the basic radical dissociates from the salt and forms a hydroxide ion (OH-). The hydroxide ion increases the pH of the solution, making it basic.

PROCESS

1. Preparation of the salt solution:
2. Dissolve a small amount of the salt sample in distilled water in a test tube.

3. Stir the solution to ensure complete dissolution of the salt.

4. Testing the pH of the solution:

5. Dip a pH paper or pH meter into the solution.

6. Record the pH of the solution.

7. Testing for the presence of basic radicals:

8. Add a few drops of dilute HCl to the solution.
9. Observe the change in color of the solution.
10. If the solution turns acidic (pH < 7), then the salt contains a basic radical.

11. If the solution remains basic (pH > 7), then the salt does not contain a basic radical.

12. Identification of the basic radical:

13. If the solution turns acidic upon addition of HCl, add a few drops of dilute NaOH to the solution until the pH becomes neutral (pH = 7).
14. Add a few drops of phenolphthalein solution to the solution.
15. If the solution turns pink, then the basic radical is a strong base.
16. If the solution does not turn pink, then the basic radical is a weak base.
17. To further identify the basic radical, you can perform flame tests or other specific tests for different metal ions.

OBSERVATIONS

• The pH of the salt solution will be basic (pH > 7).
• Upon addition of HCl, the solution will turn acidic (pH < 7).
• Upon addition of NaOH, the solution will turn neutral (pH = 7).
• Upon addition of phenolphthalein, the solution will turn pink if the basic radical is a strong base.

OBSERVATION TABLE

Salt Sample	pH of Solution	Change in pH upon Addition of HCl	Change in pH upon Addition of NaOH	Result
NaCl	7	No change	No change	Does not contain a basic radical
NaOH	12	Decreases	Increases	Contains a strong basic radical (OH-)
CaCO3	9	Decreases	Increases	Contains a weak basic radical (CO32-)

CALCULATION

The calculation of the concentration of the basic radical in the salt sample can be done using the following formula:

Concentration of basic radical = (Number of moles of basic radical) / (Volume of solution in liters)

The number of moles of basic radical can be calculated using the following formula:

Number of moles of basic radical = (Mass of salt sample in grams) / (Molar mass of salt sample)

The molar mass of the salt sample can be found in a reference book or online.

RESULTS

The experiment results will show whether the given salt sample contains a basic radical or not. If a basic radical is present, the experiment will also identify whether it is a strong or weak base.

PRECAUTIONS

• Always wear safety goggles and gloves when handling chemicals.
• Do not use concentrated acids or bases.
• Do not heat the test tube directly over the flame.
• Do not add too much acid or base to the solution, as this can lead to inaccurate results.
• Dispose of the chemicals and waste properly according to your local regulations.