Chemistry neutralisation is found in everyday life, but we seldom notice it. It plays a vital role in biological functions like maintaining the pH level of blood, as well as in many industrial processes.
Neutralisation (the reaction between acids and bases) typically produces salt and water products with a neutral pH. However, neutralisation reactions aren’t always complete or perfectly balanced; sometimes either the acid or the base dominates the reaction. There are also cases where the reaction may produce an acidic or basic salt.
As we explain in this article, many of the activities we perform on a daily basis, such as brushing our teeth, washing our hair, or cleaning the house, involve neutralisation reactions. Read on to learn more about neutralisation in chemistry, why it’s important and some common examples.
In this post:
What is neutralisation in chemistry?
Neutralisation in chemistry is the reaction between a basic and an acidic substance in an aqueous solution. Their respective pH levels (the former is above seven on the pH scale while the latter is below seven) effectively try to cancel each other out.
These types of acid-base reactions almost always produce salt and water. 
What is a neutralisation reaction?
When an acidic substance is mixed with a basic or alkaline substance in an aqueous solution, a neutralisation reaction occurs. The acidic solution donates protons, while the basic solution accepts protons. Hydronium and hydroxide ions are also removed in the process. The hydroxide ions become water molecules as they combine with the extra protons (hydrogen ions).
Generally, if the chemical reaction is perfectly balanced, the pH of the solution becomes neutral. However, when a strong acid reacts with a weak base, an acidic salt is produced instead. The opposite is also true; if a strong base reacts with a weak acid, a basic salt is produced.
- Example of a strong acid-weak base reaction – the reaction between hydrochloric acid and ammonia produces ammonium chloride, as shown below:
HCl + NH3 → NH4Cl
- Example of a strong base-weak acid reaction – acetic acid and sodium hydroxide react to produce sodium acetate, as shown below:
HC2H3O2 + NaOH → NaC2H3O2 + H2O
Common chemicals used at home
Many of the products we use for everyday household chores rely on neutralisation reactions. They’re often necessary to either control the potency of a substance or to create other desired substances. Here are some common examples:
1. Bleach
There are two types of laundry bleach products – one contains hydrogen peroxide as the main active ingredient, while the other contains sodium hypochlorite. Typically, household bleach products have a 3 – 6% sodium hypochlorite concentration by mass, which is usually sufficient to remove stains and kill microbes.
Bleach has a notoriously strong, pungent smell that can be neutralised with hydrogen peroxide, as shown in the equation below. 
NaOCl + H2O2 → O2 + NaCl + H2O
A note of caution: You should never mix highly-concentrated hydrogen peroxide with bleach as it results in a highly exothermic reaction. Follow the procedure here on how to gently neutralise the smell of bleach.
2. Methylated, turpentine & white spirits
Methylated, turpentine, and white spirits are all commonly used as paint thinners. Turpentine is a solvent derived from tree resin and consists mainly of monoterpenes α-pinene and β-pinene.
White spirits are basically petroleum hydrocarbons, while methylated spirits are ethanol mixed with methanol (also known as denatured alcohol). These substances have a strong irritating smell that can be neutralised using acetic acid.
3. Fertilisers
Many organic and inorganic fertilisers are produced using sulphuric acid. For example, ammonium sulphate is a salt produced as a byproduct of the reaction between ammonia and sulphuric acid.
NH3 + H2SO4 → (NH4)2SO4
Neutralisation reactions in everyday life
Neutralisation reactions are part of everyday life. They play a role in everything from biological systems to daily household chores and industrial processes. Here are some examples.
1. Tooth decay
When you consume sugary food or drinks, the bacteria in your mouth multiply very quickly and produce an acid as a metabolic waste product. The acid then reacts with the calcium compounds in your teeth, causing tooth decay. The good news is this can be neutralised by brushing your teeth with toothpaste. Toothpaste contains basic substances, such as calcium carbonate and aluminium hydroxide, which help to neutralise the acid. 
2. Shampoo & conditioner
Shampoos and conditioners contain basic substances like sodium lauroyl sarcosinate, sodium lauryl sulphate, and sodium laureth sulphate, which act as surfactants. These products are manufactured using neutralisation reactions to make them gentler on the scalp.
3. Stomach acid
Our stomachs produce hydrochloric acid as part of the digestion process. However, if too much acid is produced, hyperacidity may occur. The condition causes digestive discomfort and, in some cases, stomach ulcers. Hyperacidity can be remedied by taking antacids that neutralise excess acid and restore the stomach to its normal pH level (between 1.5 to 3.5). 
Antacid medications may contain one or more of the following ingredients:
- Aluminium hydroxide
- Magnesium carbonate
- Calcium carbonate
- Sodium bicarbonate
The importance of neutralisation reactions in daily life
The importance of neutralisation reactions in daily life can’t be underestimated. As we’ve seen, neutralisation reactions play a vital role in both natural biological functions and various industrial processes.
The effects of neutralisation reactions can either be destructive or beneficial, depending on the context. In medicine, neutralisation reactions can be used to treat conditions such as hyperacidity. They can also be used to remove bad smells or synthesise new materials.
Summary
Neutralisation reactions are important both in nature (including biological functions) and in human activities. From preventing tooth decay to the mass production of fertilisers, neutralisation has a crucial role to play.
