Experiment 71

Objective

To identify the presence of sodium salt in a supplied sample by observing the formation of a white precipitate with potassium pyroantimonate.

Introduction

Sodium salts, when reacted with potassium pyroantimonate, produce a white precipitate of sodium pyroantimonate. This precipitate may sometimes form more readily with the friction of a glass rod during mixing.

Chemical Reaction:

2NaCl+K₂H₂Sb₂O₇→Na₂H₂Sb₂O₇+2KCl

Materials

Chemicals

·       Sodium chloride (NaCl)

·       Potassium pyroantimonate (K₂H₂Sb₂O₇)

·       Distilled water

Apparatus:

·       Test tube

·       Test tube holder

·       Glass rod (for stirring)

Reagents:

·       Prepare a 5% solution of potassium pyroantimonate in a 250 ml beaker.

Procedure

1.    Sample Preparation: Place 5-6 ml of the sample solution in a test tube.

2.    Addition of Potassium Pyroantimonate: Add the potassium pyroantimonate solution to the test tube containing the sample.

3.    Mixing Step: Shake the solution well and mix thoroughly with a glass rod to facilitate the reaction.

4.    Observation of Results: Observe any color change or precipitate formation.

Observations

·       A white precipitate forms upon the addition of potassium pyroantimonate, indicating the presence of sodium ions.

Questions

1.    What is a sodium salt?

2.    How is the presence of sodium identified?

3.    What reagent is used in the sodium test?

4.    What color is observed in the sodium test?