Sodium hydroxide, NaOH has the common name of caustic soda. Here, we will study about the preparation, properties and uses of sodium hydroxide, (Caustic soda)
Introduction of Sodium Hydroxide (Caustic Soda), NaOH
- Crystalline Sodium hydroxide dissolves in water to form strongly alkaline solution.
- Sodium hydroxide solution decomposes proteins and lipids in living tissues.
- NaOH is an alkali salt also known as Lye.
Preparation of NaOH by Castner-Keller cell
There is a large rectangular iron tank. Ionisation of NaCl takes place on passing electricity through it.
Outer compartments :
- NaCl shows complete dissociation as it is a strong electrolyte.
NaCl ……………> Na+ + Cl-
Ionisation of H2O as a weak electrolyte takes place :
H2O …………………..> H+ + OH-
Cl- and OH- anions migrate towards the graphite rod but cations Na+ and H+ move towards Hg electrode.
2. At the anode : The discharge potential of Cl- ions is lower than that of OH-
Therefore, Cl2 gas is liberated at anode and OH- ions remains in the solution.
Cl- ……………………> Cl + e-
Cl + Cl ………………… > Cl2 (anode)
3. At the cathode : The discharge potential of Na+ is lower than that of H+ Therefore, Na+ ions are discharged on cathode.
Na+ + e- …………………> Na
2Na + xHg ………………….> Na2HgX (Sodium amalgam)
Central Compartment :
- NaOH ……………. Na+ + OH- H2O ……………….. H+ + OH-
2. At the Cathode : Here, the discharge potential of H+ is lower than Na+
H+ + e- ………………….> H H + H …………………………….> H2
Properties of Sodium Hydroxide, NaOH
- NaOH is a white crystalline solid having a melting point of 591 K
- Sodium hydroxide is highly soluble in water and gives strong alkaline solution.
- Caustic soda is bitter in taste and corrosive in nature
- Sodium hydroxide crystals are deliquescent that is absorbs moisture and dissolves in the water.
- NaOH solution reacts with carbon dioxide to form sodium carbonate.
- Sodium hydroxide finds application in the purification of bauxite.
Uses of Sodium Hydroxide, NaOH
1. Caustic soda is used in the manufacturing of paper, soap and rayon.
2. Use NaOH in the preparation of fats and oils.
3. NaOH finds utilisation in the purification of bauxite.
4. Use NaOH in the manufacturing of dyes and many other chemicals laboratory reagent.
5. Textile industry uses NaOH for mercerising cotton fabrics.
6. Petroleum refining industry also uses sodium hydroxide.
7. Use NaOH in the preparation of soda lime and washing soda.
FAQ’s related to Sodium hydroxide, NaOH
- Is sodium hydroxide used for cleaning?
Answer : Sodium hydroxide is a cleansing agent to remove dirt and grease.
2. What is sodium hydroxide not used for?
Answer: Sodium hydroxide is not used in plastic industry.
3. Does sodium hydroxide melt easily?
Answer: Sodium hydroxide in the pure form is crystaline colourless solid. It is highly soluble in water and melts at 318°C without decomposition.
Check out the structure of NH3 here
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