Definition of Neutralisation
Neutralisation Reaction: Neutralisation is a special kind of chemical process that happens when an acid and a base are mixed together. When they meet, the acid and base cancel out each other’s strong properties. As a result, two new products are formed: salt and water. This chemical change reduces the strength of the acid and the base, making the final solution neither too acidic nor too basic.
Process of Neutralisation
Ion Reaction: In a neutralisation reaction, the tiny charged particles from the acid and base, called ions, come together. The hydrogen ions (H⁺) from the acid react with the hydroxide ions (OH⁻) from the base. When they combine, they form neutral water molecules (H₂O), removing the acidic and basic properties.
Acid Dissociation: When acids are put into water, they break apart, or dissociate, into smaller pieces called ions. For example, hydrochloric acid (HCl) separates into hydrogen ions (H⁺) and chloride ions (Cl⁻) when it dissolves in water, making the solution acidic.
Base Dissociation: Bases behave in a similar way when dissolved in water. For instance, sodium hydroxide (NaOH) splits into sodium ions (Na⁺) and hydroxide ions (OH⁻) when it dissolves. The hydroxide ions are what give bases their special properties.
Formation of Water: During a neutralisation reaction, the hydrogen ions (H⁺) from the acid and the hydroxide ions (OH⁻) from the base join together to make water molecules (H₂O). This combination helps remove the acidic and basic properties from the solution.
Effect on pH: Neutralisation changes the pH of the solution by reducing the amount of free hydrogen ions and hydroxide ions. This process pushes the pH closer to 7, which is the value for a neutral solution that is neither acidic nor alkaline.
Neutralisation Indicators
pH of Neutral Solution: A solution that has gone through complete neutralisation will have a pH value of exactly 7. This means it is balanced—not acidic and not basic.
Litmus Paper Indicator: Litmus paper is a simple way to test if a solution is acidic, neutral, or alkaline. In a neutral solution, litmus paper turns purple. If the solution is acidic, it turns red. If it is alkaline, it turns blue.
General Indicators: Scientists often use other indicators like methyl orange and phenolphthalein. These special dyes change colour depending on the pH of the solution, helping us see when neutralisation has occurred.
Hydrogen Ion Concentration: When there are a lot of hydrogen ions in a solution, it becomes very acidic. If the number of hydrogen ions decreases, the solution becomes less acidic and moves closer to being neutral.
Hydroxide Ion Concentration: A solution with many hydroxide ions is very alkaline. If the number of hydroxide ions goes down, the solution becomes less alkaline and closer to neutral.
Titration
Purpose of Titration: Titration is a careful lab method used to find out the exact concentration of an acid or a base. This is done by reacting it with a solution of known concentration until neutralisation is complete.
Titration Apparatus: Scientists use special equipment for titration, like burettes to add one solution slowly, pipettes to measure exact amounts, and conical flasks to mix the solutions properly.
Role of Indicators: Indicators are added during titration to signal when neutralisation is finished. They do this by changing colour exactly at the moment the acid and base balance each other.
Importance of Indicators: The colour change shown by the indicator helps scientists know the exact point when the reaction is complete. This makes the measurements accurate and reliable.
Calculations
Titration Formula: In titration calculations, we use the formula M₁V₁/a = M₂V₂/b. Here, “M” stands for molarity (the concentration of the solution), “V” stands for volume, and “a” and “b” are numbers from the balanced equation showing how many moles are involved.
Meaning of M and V: In the formula, M is the concentration (how strong the solution is), and V is the volume (how much solution is used). M₁ and V₁ represent the acid, while M₂ and V₂ represent the base.
Stoichiometric Coefficients: The letters ‘a’ and ‘b’ come from the balanced chemical equation. They tell us how many parts (moles) of acid and base are needed to react perfectly.
Balancing Equations: It is very important to balance the chemical equation before starting calculations. A balanced equation makes sure that we know the correct ratios of acid to base.
Finding Unknown Molarity: After performing the titration and reaching neutralisation, you can use the data collected along with the titration formula to find out the molarity (concentration) of the unknown solution.
Identifying End-point: The end-point of a titration is the exact moment when neutralisation has finished. This is usually shown clearly by a colour change in the indicator, telling you to stop adding more solution.
Types of Neutralisation Reactions
Acid + Metal Hydroxide: When an acid reacts with a metal hydroxide, the result is salt and water. For example, hydrochloric acid (HCl) reacting with sodium hydroxide (NaOH) forms sodium chloride (NaCl) and water (H₂O).
Acid + Metal Oxide: An acid can also react with a metal oxide to form a salt and water. For instance, hydrochloric acid (HCl) reacts with copper(II) oxide (CuO) to produce copper(II) chloride (CuCl₂) and water (H₂O).
Acid + Metal Carbonate: When an acid reacts with a metal carbonate, it forms three products: a salt, water, and carbon dioxide gas. A good example is hydrochloric acid (HCl) reacting with sodium carbonate (Na₂CO₃), which produces sodium chloride (NaCl), water (H₂O), and carbon dioxide (CO₂).
Acid + Ammonia: An acid can also react with ammonia (NH₃) to produce a salt. For example, hydrochloric acid (HCl) reacts with ammonia to form ammonium chloride (NH₄Cl).
Applications of Neutralisation
Use in Antacids: In medicine, antacids are used to help people who have too much acid in their stomachs. Antacids contain alkaline substances like magnesium hydroxide that neutralise the excess stomach acid and bring relief.
Use in Agriculture: Farmers use neutralisation to improve soil. If the soil is too acidic, they add lime, an alkaline material, to raise the pH and make the soil better for growing crops.
Bee Sting Treatment: Bee stings are acidic, and applying a mild alkali like sodium hydrogen carbonate (baking soda) can neutralise the sting, making the pain less severe.
Industrial Applications: In factories, neutralisation is very important to control the pH levels during chemical processes. This helps keep equipment safe and ensures that products are made correctly.
Water Treatment: In water treatment plants, neutralisation is used to adjust the pH of water to make it safe for drinking and to protect pipes and machines from being damaged by acids or alkalis.