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In our lower classes, we studied the neutralisation reaction.
When an acid and a base combine, a chemical reaction occurs, resulting in the formation of salt and water. The procedure is known as a neutralisation reaction.
The salt produced here can be acidic, basic, or neutral. The reaction mixture heats up as a result of neutralisation, which is an exothermic reaction.
\(Acid + Base \xrightarrow [reaction] {exothermic}Salt + Water\)
Let us now prove the neutralisation reaction with the help of an experiment:
Example:
Activity 1:
To explain how acid and base react with each other.
Apparatus required:
- Test tubes
- Sodium hydroxide \(NaOH\)
- Hydrochloric acid \(HCl\)
- Phenolphthalein indicator (colourless solution)
- Dropper
Step 1: Take a test tube and add about \(2ml\) of dilute sodium hydroxide \(NaOH\) solution.
Step 2: Add \(2\) drops of phenolphthalein indicator to it.
Step 3: Observe the changes.
- We can now find that the colour of the solution changes to pink.
Step 4: Add dilute hydrochloric acid \(HCl\) solution drop by drop to the above test tube.
Step 5: Observe the changes.
- The colour of the solution turns colourless after the addition of acid to it.
Step 6: Again, add a few drops of dilute sodium hydroxide \(NaOH\) solution.
Step 7: Observe the changes.
- The colourless solution again changes into pink colour.
Observation:
- Here \(HCl\) has neutralized the \(NaOH\) solution and vice versa
- We have also seen the changes in the colour of the solution.
Result: In the final solution that is present in the test tube contains salt and water.
The chemical reaction for the above experiment can therefore be written as
\(NaOH + HCl \rightarrow NaCl + H_2O\)
In general, the neutralisation reaction can be written as
\(Acid + Base \rightarrow Salt + Water\)
Note: Phenolphthalein is a weak acid and a colourless solution, but its ions are pink. If hydrogen ions are added, which is present in acids added to the pink solution, the equilibrium will switch, and the solution turns colourless. This is the reason why phenolphthalein changes its colour when acid is added to the pink solution.
Therefore due to this reason, phenolphthalein has no effect on acid but changes to pink colour in the presence of a base.
Let us also see some of the uses of acids and bases:
Uses of acids:
- The "King of Chemicals" is sulphuric acid since it is used to make so many other compounds. It is also used in car batteries.
- In toilets, hydrochloric acid is used as a cleaning agent.
- Citric acid is used to make effervescent salts and is also used as a food preservative.
- Fertilizers, dyes, colours and medicines are all made with nitric acid.
- Iron and manganese deposits on quartz crystals are removed with oxalic acid. It is also used to remove black stains and as wood bleach.
- In aerated beverages, carbonic acid is used.
- Baking powder has tartaric acid as a component.
- Our stomachs generate hydrochloric acid, which helps in the digestion of food.
- Vinegar contains acetic acid, which is used to preserve food.
- Benzoic acid is also used in the preservation of foods such as pickles.
- Important laboratory reagents include hydrochloric acid, nitric acid and sulphuric acid.
- Nucleic acids are the essential nuclear substance found in all living creatures' cells.
- Deoxyribonucleic acid (DNA) is found in animals, whereas ribonucleic acid (RNA) is found in plants.
- Pickles remain in good condition for a long time due to the presence of vinegar (acetic acid) or benzoic acid.
Uses of bases:
- Buildings are whitewashed with calcium hydroxide.
- Magnesium hydroxide is a drug that is used to treat stomach problems.
- Grease stains on clothing are removed with ammonium hydroxide.
- Sodium hydroxide is used to make washing soaps, also used in paper industries, textile industries and medicines.
- Aluminium hydroxide and magnesium hydroxide are used in antacids to cure acidity problems.
- Ammonium hydroxide is used to manufacture fertilizers, nylon, Plastics and Rubber.
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