Syllabus covered in the MSVgo app

Free Unlimited Access till 31st March, 2021

Download Now

Chapter 18 – Preparation of Sodium Hydroxide

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:

Introduction

Preparation of Sodium Hydroxide is an essential industry practice. Sodium Hydroxide, or NaOH, is a strong alkali manufactured by electrolysis of brine (NaCl – common salt) solution. You must have seen the solid white crystals of sodium hydroxide in the labs. You must have felt the crystal being slippery to the touch (hence saponification – manufacture of soap). NaOH reacts with the skin’s natural oils.

It is also known as lye or caustic soda. It possesses a corrosive nature that can harm animals and plant tissues. It is used in paper and pulp, water treatment, textiles, and soap and detergent manufacture.

There are three primary methods to prepare caustic soda: the Castner-kellner process, the Nelson Diaphragm process, and Loewig’s process.

NaOH is a byproduct of the chlorine extraction process. It is generally made in an industrial process known as the Chloralkali process. This process is easy electrolysis of brine water (aqueous NaCl). We shall study this process in more detail.

The diaphragm cell contains two separate compartments where the brine water is poured down. The two containers have a titanium anode and steel cathode, respectively. Yes, it may be a little surprising, but titanium cathode is being used in this device because it prevents corrosion by chlorine.

As we all know that reduction occurs at the cathode, and oxidation occurs at the anode in electrochemistry. Hence, NaCl dissociates into ions in the given solution.

NaCl(aq)→Na+(aq)+Cl−(aq)

The H2O(l) can also dissociate into:

H2O(l)⇌H+(aq)+OH−(aq)

When the current is passed through the solution, the anions are attracted to the anode. The cations are attracted to the cathode. In the anode, there is a competition between the OH−(aq) and the Cl−(aq) ions. Cl−(aq) wins because it is easier to discharge.

Similarly, there is a competition between the Na+(aq) and the H+(aq) ions at the cathode. H+(aq) wins because it is easier to discharge.

So, we can now write the equation at the cathode as:

2Cl−(aq)→Cl2(g)+2e−

And the equation at the anode as:

2H+(aq)+2e−→H2(g)

These ions get discharged at the electrodes, and remaining ions are present in the solution that makes the sodium hydroxide.

Some of the properties of sodium hydroxide are given below.

  • NaOH is a white colored solid that has a high melting point of 591K.
  • It feels soapy to touch and is bitter. Although it is a stable compound, NaOH possesses corrosive nature.
  • It is highly alkaline and is water-soluble.
  • It is used as a cleansing agent due to its corrosive cleaning properly.

It’s a strong base and a salt at the same time!

A salt is an ionic compound consisting of a metal and a nonmetal. The metal is sodium, and the acid is water (aka hydroxylic acid). Water’s corresponding base is OH(-).

Na(+)OH(-) is just a salt like Na(+)Cl(-) or Na2SO4 or NaHSO4.

·NaOH is a very alkaline salt. This salt exists in countless modifications, including several hydrates, like Orthorhombic NaOH Space group: Cmcm, No. 63.

Sodium hydroxide has some distinguishable physical properties. They are given below:

  • They appear as pellets of white color.
  • Their boiling point is 140 degrees C for a 40% aqueous solution.
  • Molecular weight is 39.997 g/mol.
  • Specific gravity is 1.5.

Let’s check some uses of sodium hydroxide.

  • It is used as an essential chemical reagent in laboratories.
  • Soda-lime is prepared using sodium hydroxide.
  • Aluminum is extracted from bauxite with the help of sodium hydroxide.

Caustic soda / sodium hydroxide is a very alkaline compound that can have corrosive effects on animals or plant tissues. They are extensively used for cleaning purposes as a washing powder or to remove stains from drains or floors. Preparation of sodium hydroxide can be done in different ways. The widely used method is the electrolysis of the brine solution.

  1. How is sodium hydroxide prepared?

The synthesis starts from the electrolysis of ultra-pure Sodium Chloride (a highly purified table salt). Sodium and chlorine are separated immediately; while chlorine can be employed for several different reactions (mainly depending on market demands and prices), sodium reacts with water to form NaOHor Sodium Hydroxide, which comes out from the reactor in an aqueous solution of 50%. The solid form (pellets, prills, or flake) requires heat treatment to dry the solution.

The most extensive part of the production is the energy needed for the electrolysis. The means to separate chlorine and sodium used to be a mercurial cell reaction; nowadays, a particular membrane is used in modern reactors.

  1. How is NaOH prepared from NaCl?

The process is called the Castner- Kellner process, where we do the electrolysis of the brine solution (NaCl) to get our desired result of sodium hydroxide.

  1. Where is sodium hydroxide found?

You can buy sodium hydroxide from shops, including hardware shops or grocery markets. It is also called caustic soda in general terms.

  1. What is sodium hydroxide lye used for?

You can use it to strip paint, unclog drains, and make soap. Also, use it with hydrogen peroxide (30% hydrogen peroxide) to make homemade wood bleach. Another possible home use is the preparation of foods such as hominy, some pretzels, and cleaning.

  1. What are the sources of sodium hydroxide?

Sea Water (Brine) electrolysis, and you can also get it using advanced membrane technology. Or simply buy it from your nearby hardware shop.

You can learn about the manufacturing process of sodium hydroxide through explanatory videos available on MSVgo.

High School Physics

  • Alternating Current
  • Atoms
  • Communication Systems
  • Current Electricity
  • Dual nature of Radiation and Matter
  • Electric Charges and Fields
  • Electricity
  • Electromagnetic Induction
  • Electromagnetic Waves
  • Electron Beams and Radioactivity
  • Electrons and Photons
  • Electrostatic Potential and Capacitance
  • Fluid Pressure
  • Force and Acceleration
  • Force And Laws Of Motion
  • Gravitation
  • Internal Energy
  • Kinetic Theory
  • Law of motion
  • Light – Reflection And Refraction
  • Magnetic Effects Of Electric Current
  • Magnetism and Matter
  • Management Of Natural Resources
  • Mechanical properties of Fluids
  • Mechanical properties of Solids
  • Motion
  • Motion in a plane
  • Motion in a straight line
  • Moving Charges and Magnetism
  • Nuclear Energy
  • Nuclei
  • Oscillations
  • Our Environment
  • Paths of Heat
  • Physical world
  • Ray optics and optical instruments
  • Semiconductor Devices
  • Semiconductor Electronics: Materials, Devices and Simple Circuits
  • Simple Machines
  • Sound
  • Sources Of Energy
  • Specific and Latent Heats
  • Spherical Mirrors
  • Static Electricity
  • Systems of Particles and Rotational motion
  • Thermal properties of matter
  • Thermodynamics
  • Units and Measurement
  • Vectors, Scalar Quantities and Elementary Calculus
  • Wave Optics
  • Waves
  • Work, Power and Energy

High School Chemistry

  • Acids, Bases and Salts
  • Alcohols, Phenols and Ethers
  • Aldehydes, Ketones and Carboxylic Acids
  • Aliphatic and Aromatic Hydrocarbons
  • Alkyl and Aryl Halides
  • Amines
  • Analytical Chemistry 
  • Atomic Structure
  • Atoms And Molecules
  • Basic concepts of Chemistry
  • Biomolecules
  • Carbon And Its Compounds
  • Carboxylic acids and Acid Derivatives
  • Chemical Bonding and Molecular Structures
  • Chemical Energetics
  • Chemical Equilibria
  • Chemical Kinetics
  • Chemical Reactions And Equations
  • Chemical Reactions and Their Mechanisms
  • Chemistry in Everyday Life
  • Chemistry of p-Block elements
  • Chemistry of Transition and Inner Transition
  • Classification of Elements
  • Coordination Compounds
  • Cyanide, Isocyanide, Nitro compounds and Amines
  • Electrochemistry
  • Electrolysis
  • Elements, Compounds and Mixtures
  • Environmental Chemistry
  • Equilibrium
  • Ethers and Carbonyl compounds
  • Haloalkanes and Haloarenes
  • Hydrocarbons
  • Hydrogen
  • Ideal solutions
  • Introduction to Organic Chemistry
  • Ionic equilibria
  • Matter
  • Matter Around Us
  • Matter In Our Surroundings
  • Metallurgy
  • Metals And Non-Metals
  • Mole Concept and Stoichiometry
  • Natural Resources
  • Organic Chemistry – Basic Principles
  • Periodic Classification of Elements
  • Physical and Chemical Changes
  • Physical and Chemical Properties of Water
  • Polymers
  • Preparation, Properties and Uses of Compounds
  • Principles and Processes of Isolation of Elements
  • Redox Reactions
  • Relative Molecular Mass and Mole
  • States of Matter
  • Structure Of The Atom
  • Study of Compounds
  • Study of Gas Laws
  • Study of Representative Elements
  • Surface Chemistry
  • The d-block and f-block elements
  • The Gaseous State
  • The p-Block Elements
  • The Periodic Table
  • The s-Block Elements
  • The Solid State
  • Thermodynamics

High School Biology

  • Absorption and Movement of Water in Plants
  • Adolescent Issues
  • Anatomy of Flowering Plants
  • Animal Kingdom
  • Bacteria and Fungi-Friends and Foe
  • Biodiversity and Conservation
  • Biofertilizers
  • Biological Classification
  • Biomedical Engineering
  • Biomolecules
  • Biotechnology and its Applications
  • Biotic Community
  • Body Fluids and Circulation
  • Breathing and Exchange of Gases
  • Cell – Unit of Life
  • Cell Cycle and Cell Division
  • Cell Division and Structure of Chromosomes
  • Cell Reproduction
  • Cellular Respiration
  • Chemical Coordination and Integration
  • Circulation
  • Control And Coordination
  • Crop Improvement
  • Digestion and Absorption
  • Diversity In Living Organisms
  • Ecosystem
  • Environmental Issues
  • Excretory Products and their Elimination
  • Flowering Plants
  • Genes and Chromosomes
  • Health and Diseases
  • Health and Its Significance
  • Heredity And Evolution
  • Heredity and Variation
  • How Do Organisms Reproduce?
  • Human Diseases
  • Human Eye And Colourful World
  • Human Health and Disease
  • Human Population
  • Human Reproduction
  • Hygiene
  • Improvement In Food Resources
  • Integumentary System- Skin
  • Kingdom Fungi
  • Kingdom Monera
  • Kingdom Protista
  • Life Processes
  • Locomotion and Movement
  • Microbes in Human Welfare
  • Mineral Nutrition
  • Molecular Basis of Inheritance
  • Morphology of Flowering Plants
  • Neural Control And Coordination
  • Nutrition in Human Beings
  • Organism and Population
  • Photosynthesis
  • Photosynthesis in Higher Plants
  • Plant Growth and Development
  • Plant Kingdom
  • Pollination and Fertilization
  • Pollution; Sources and its effects
  • Principles of Inheritance and Variation
  • Reproduction and Development in Angiosperms
  • Reproduction in Organisms
  • Reproductive Health
  • Respiration in Human Beings
  • Respiration in Plants
  • Respiratory System
  • Sexual Reproduction in Flowering Plants
  • Strategies for Enhancement in Food Production
  • Structural Organisation in Animals
  • Structural Organisation of the Cell
  • The Endocrine System
  • The Fundamental Unit Of Life
  • The Living World
  • The Nervous System and Sense Organs
  • Tissues
  • Transpiration
  • Transport in Plants

High School Math

  • Algebra – Arithmatic Progressions
  • Algebra – Complex Numbers and Quadratic Equations
  • Algebra – Linear Inequalities
  • Algebra – Pair of Linear Equations in Two Variables
  • Algebra – Polynomials
  • Algebra – Principle of Mathematical Induction
  • Algebra – Quadratic Equations
  • Binomial Theorem
  • Calculus – Applications of Derivatives
  • Calculus – Applications of the Integrals
  • Calculus – Continuity and Differentiability
  • Calculus – Differential Equations
  • Calculus – Integrals
  • Geometry – Area
  • Geometry – Circles
  • Geometry – Conic Sections
  • Geometry – Constructions
  • Geometry – Introduction to Euclid’s Geometry
  • Geometry – Three-dimensional Geometry
  • Geometry – Lines and Angles
  • Geometry – Quadrilaterals
  • Geometry – Straight Lines
  • Geometry – Triangles
  • Linear Programming
  • Matrices and Determinants
  • Mensuration – Areas
  • Mensuration – Surface Areas and Volumes
  • Number Systems
  • Number Systems – Real Numbers
  • Permutations and Combinations
  • Probability
  • Sequence and Series
  • Sets and Functions
  • Statistics 
  • Trignometry – Height and Distance
  • Trignometry – Identities
  • Trignometry – Introduction

Middle School Science

  • Acids, Bases And Salts
  • Air and Its Constituents
  • Basic Biology
  • Body Movements
  • Carbon and Its Compounds
  • Cell – Structure And Functions
  • Changes Around Us
  • Chemical Effects Of Electric Current
  • Chemistry in Your Life
  • Coal And Petroleum
  • Combustion And Flame
  • Components Of Food
  • Conservation Of Plants And Animals
  • Crop Production And Management
  • Electric Current And Its Effects
  • Electricity And Circuits
  • Elements and Compounds
  • Fibre To Fabric
  • Food production and management
  • Force And Pressure
  • Forests: Our Lifeline
  • Friction
  • Fun With Magnets
  • Garbage In, Garbage Out
  • Getting To Know Plants
  • Health and Hygiene
  • Heat
  • Hydrogen
  • Life Processes: Nutrition in Animals and Plants
  • Light, Shadows And Reflections
  • Materials: Metals And Non-Metals
  • Matter and Its States
  • Metals and Non-metals
  • Micro Organisms: Friend And Foe
  • Motion And Measurement Of Distances
  • Motion And Time
  • Nutrition In Animals
  • Nutrition In Plants
  • Organization in Living Things
  • Our Environment
  • Physical And Chemical Changes
  • Pollution and conservation
  • Pollution Of Air And Water
  • Reaching The Age Of Adolescence
  • Reproduction In Animals
  • Reproduction In Plants
  • Respiration In Organisms
  • Rocks and Minerals
  • Separation Of Substances
  • Simple Machines
  • Soil
  • Some Natural Phenomena
  • Sorting Materials Into Groups
  • Sound
  • Stars And The Solar System
  • Structure of Atom
  • Synthetic Fibers And Plastics
  • The Living Organisms And Their Surroundings
  • Transfer of Heat
  • Transformation of Substances
  • Transportation In Animals And Plants
  • Universe
  • Waste-water Story
  • Water: A Precious Resource
  • Weather, Climate And Adaptations Of Animals To Climate
  • Winds, Storms And Cyclones

Middle School Math

  • Addition
  • Area and Its Boundary
  • Boxes and Sketches
  • Data Handling
  • Fun With Numbers
  • Heavy and Light
  • How Many
  • Long And Short
  • Mapping
  • Measurement
  • Money
  • Multiplication and Factors
  • Multiply and Divide
  • Numbers
  • Parts and Wholes
  • Pattern Recognition
  • Patterns
  • Play With Patterns
  • Rupees And Paise
  • Shapes And Angles
  • Shapes And Designs
  • Shapes and Space
  • Similarity
  • Smart Charts
  • Squares
  • Subtraction
  • Tables And Shares
  • Tenths and Hundredths
  • Time
Please switch to portrait mode
for the best experience.
Click to open Popup