Preparation of Sodium hydroxide Class 10

If you are looking for a preparation method for sodium hydroxide, and its uses, then this is for you.

This topic belongs to Chapter 2 Acids, bases, and salts class 10 science NCERT book.

Table of Contents

 

 1. What is Sodium Hydroxide?

 2.Properties of Sodium hydroxide

 3. Preparation methods of Sodium Hydroxide

 4. Uses of Sodium Hydroxide

 5. Safety Precautions

 6. Quiz

 7.  Important Questions

 8.FAQs

 9. Related Topics

 

Preparation Process of NaOH

 

What is Sodium Hydroxide?

Sodium hydroxide is a strong base and also an alkali. Its common name is Caustic soda and its chemical formula is NaOH.

Properties of sodium hydroxide

   1.  It is a white crystalline solid.

   2.  It is highly corrosive

   3.  It is odourless

   4.  It is soluble in water

   5.  Inorganic compound

   6.  Its melting point is 591K

   7. Its crystals are hygroscopic

Preparation methods of Sodium hydroxide

Sodium hydroxide can be prepared by following methods

1: Castner-Kellner Process

 2: Chlor-Alkali Process

In this topic, we will discuss the preparation of sodium hydroxide by the chlor-alkali process.

Chlor-alkali Process (Class 10)

Raw materials: - Sodium chloride (NaCl) and water

Principle: - Sodium hydroxide is prepared by electrolysis of a solution of sodium chloride(brine).

Preparation of brine: - Saturated solution of sodium chloride is called brine. So NaCl is mixed in water to produce brine.

Electrolysis of brine

Electrolysis of a concentrated solution of sodium chloride(brine) is done in an electrolytic cell which is known as a ‘Diaphragm cell’. When an electric current is passed through the brine, ionization of NaCl takes place.

Chloride ions move towards the anode and sodium ions move towards the cathode.

Chlor-alkali Process

Chlor  alkali process equation

`2NaCl + 2H_2O →2NaOH_{(aq)} + Cl_{2(g)} + H_{2(g)}`

The above chlor -alkali equation is carried out as follows

Ionization of NaCl 

 `NaCl(aq)  →  2Na^+  + 2Cl^-`

                 (at Cathode)  (at anode)

 

Sodium chloride gets ionized into sodium and chloride ions

Ionization of `H_2O`

`2H_2O →   2H^+   +   2OH^-`

            (at Cathode)     (at anode)

Water gets decomposed into hydrogen and hydroxyl ions

Electrochemical changes

At cathode     `2H^+  +2e^-  → H_{2(g)}`

Hydrogen ions are reduced to hydrogen gas by accepting electrons.

At anode        `2Cl^-    → Cl_2  +  2e^-`

Chloride ions are oxidized to chlorine gas by losing electrons.

In solution     `2Na^+  +  2OH^-   →   2NaOH`

Sodium ions and hydroxyl ions accumulate in the solution. On evaporation. Sodium hydroxide is obtained.

`2NaCl + 2H_2O →2NaOH_{(aq)} +  Cl_{2(g)} + H_{2(g)}`

The products of the chloralkali process are 

i). chlorine gas

ii). Hydrogen gas

iii). Sodium hydroxide

Uses  of Sodium Hydroxide(Caustic soda)

The following are the most important uses of sodium hydroxide

   1.  In the manufacturing of soap and detergents

   2.  In degreasing metal sheets and rods

   3.  In textile industries

   4.  In the synthesis of artificial fibers

   5.  In paper making

   6.  As a laboratory reagent

    Uses of Chlorine gas

   1.  In the manufacturing of chloroform, bleaching powder, HCl

    2.  For water treatment

    3.  In the manufacturing of PVC

    4.  In manufacturing pesticides

    5.  In making CFC

 

Uses of hydrogen gas

   1.  In making vegetable ghee (hydrogenation process)

   2.  In manufacturing ammonia

   3.  As fuel used in rockets

   4.  In making margarine

    Safety Precautions

   1.  Always wear goggles, a lab coat

   2.  Protect eyes, skin

   3.  Avoid direct contact with NaOH

     

    Quiz

   

Important questions

Q1. Why sodium hydroxide is called caustic soda?

Ans.- The word ‘Caustic’ means burning or corrosive nature and it burns living tissues so sodium hydroxide is called caustic soda.

Q2. Why sodium hydroxide is called an alkali?

Ans. -  The base which is soluble in water is called alkali and sodium hydroxide is soluble in water.

Q3. What is brine?

Ans. – A saturated sodium chloride solution is called brine.

Q4. Why mixing of NaOH in water an exothermic reaction?

Ans. – When sodium hydroxide is mixed in water, it dissociates into sodium ions and hydroxyl ions and heat is liberated so this is an exothermic reaction.

Q5. What type of compound is sodium hydroxide?

Ans. – Sodium hydroxide  is an inorganic ionic compound

Q6. What is formed when zinc reacts with sodium hydroxide?

Ans. – When zinc reacts with sodium hydroxide, sodium zincate, and hydrogen gas are produced.

          

  `Zn + 2NaOH → Na_2ZnO_2 + H_2`

 

 Q7. Why sodium hydroxide preparation method is called the chlor alkali method?

Ans- In this process, one product is chlorine and the other is sodium hydroxide which is an alkali so this process is called the chlor alkali method.

Q8. How is NaOH prepared from sodium chloride?

Ans - When an electric current is passed through an aqueous solution of sodium chloride, it decomposed to form sodium hydroxide. Chlorine and hydrogen gases are also produced.

FAQs (Frequently Asked Questions)

   1.  What is the formula for sodium hydroxide?

 Ans – NaOH

    2.  The reaction between sodium hydroxide and hydrochloric acid is considered what type of reaction?

Ans -  The reaction between sodium hydroxide and hydrochloric acid is a neutralization reaction.

    3.  What type of solution is formed when solid sodium hydroxide (NaOH) is dissolved in water?

Ans – Sodium hydroxide is an ionic substance when it is dissolved in water, it gets dissociates into ions and forms an ionic alkaline solution.

   4.  What is the molecular weight of sodium hydroxide (NaOH)?

    Ans – The molecular weight of sodium hydroxide is 40.

    5.  What is the molar mass of sodium hydroxide, NaOH?

Ans - 39.997 g/mol

 

         Related Topics

    1. Physical Properties of Metals

    2. Preparation of Baking Soda

3. Preparation of Washing  Soda