Question

Write the procedure for the formation of Sodium sulfate crystals.

Answer 1

Part 1: Reaction:-

1. Sodium sulfate (Na₂SO₄) is prepared by the neutralization reaction of Caustic soda with dilute Sulphuric acid.
2. $$\begin{gathered} 2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ (\mathrm{Caustic}\mathrm{soda})(\mathrm{Dilute}\mathrm{Sulphuric}\mathrm{acid})(\mathrm{Sodium}\mathrm{sulfate})\left(\mathrm{Water}\right) \end{gathered}$$

Part 2: Procedure:-

1. The formation of Sodium sulfate (Na₂SO₄) is a neutralization reaction, therefore, a titration is performed.
2. Take 25ml/cm³ of Sodium hydroxide (caustic soda) (NaOH) in a conical flask.
3. A phenolphthalein indicator is added. (an indicator is used to detect the endpoint of a neutralization reaction.)
4. After adding the indicator, the solution color will change to pink.
5. A burette is filled with dilute Sulphuric acid (dilute Sulphuric acid is prepared by adding 1000 ml of water into 10 ml of concentrated Sulphuric acid.)
6. Note the reading of the burette.
7. Turn on the tap and slowly allow the acid to run into the conical flask.
8. Note the point on the burette when the conical flask solution becomes colorless.
9. The solution got in the flask is Sodium sulfate (Na₂SO₄) and water.
10. After heating the solution, we get pure Sodium sulfate crystals (Na₂SO₄.10H₂O).