We have learned that acids taste sour and turn blue litmus red. Whereas, a base tastes bitter and turns red litmus blue. Can you imagine, what will happen if acid and base are mixed together? Neutralization reaction happens! Let us learn what is it? Before we go ahead let us know about an acid-base indicator known as phenolphthalein.

 

Phenolphthalein is a colorless liquid. Its color changes to pink when added to a basic solution. With acids, it shows no change in color.

 

Activity:-

 

1. Take a small quantity of dilute hydrochloric acid in a beaker. Add 2-3 drops of phenolphthalein to the acid. Stir the liquid with a glass rod. Using a dropper add a drop of sodium hydroxide solution to the acid solution. What do you observe?
2. The pink color appears and then immediately disappears. Keep stirring the acid solution and continue adding sodium hydroxide drop by drop. A time will come when the pink color takes a large time to disappear. Add carefully only one drop of the base at a time. Stir the acid solution after each drop of the base is added.
3. As soon as the faint pink color becomes permanent, stop adding the base.
4. Now add just one drop of hydrochloric acid to the liquid in the beaker and observe. The pink color disappears.
5. It is evident from this activity that phenolphthalein gives pink color in basic solutions and with the acidic solution it remains colorless. Again add one drop of the base sodium hydroxide to the solution in the beaker. Solution in the beaker again becomes pink in color.

 

It is very important to note from this Activity that acid and base neutralize the effect of each other.

 

When an acidic solution is mixed with a basic solution, the resulting solution may be acidic, basic, or neutral depending on the amount of acidic and basic solutions mixed. When an acid solution and a base solution are mixed in the right amount, both the basic nature of the base and the acidic nature of the acid are neutralized or destroyed. The resulting solution is neither acidic nor basic. It is neutral.

 

If one touches the tube immediately after the neutralization process one feels hot. In a neutralization reaction heat is always produced. When an acid reacts with a base, a new substance is produced. This new substance is called salt. Salt may be acidic, basic, or neutral.

 

For example; Copper sulfate is an acidic salt, washing soda is a basic salt and common salt is a neutral salt. The reaction between an acid and a base is known as neutralization. Salt and water are produced in the process with the evolution of heat. So we can write the equation of neutralization as:-

 

Acid + Base = salt + water+ heat

 

Neutralization reaction between hydrochloric acid and sodium hydroxide can be written as

 

Hydrochloric acid + sodium hydroxide = sodium chloride + water + heat evolved.

 

Uses of Neutralization Reaction

 

The process of neutralization is used in everyday life to cure many ailments. Let us see some of the cases, where it is used :-

 

To treat gastric patients

 

Our stomach contains hydrochloric acid. It helps in digestion of the food. But excess acid in stomach causes indigestion and acidity. To relieve indigestion we take anti-acids. Anti acids or antacids are medicines containing bases such as aluminum hydroxide and magnesium hydroxide to neutralize the excess acid in the stomach.

 

To treat ant bites

 

Ant bites and bee stings are acidic in nature. When ant bites, it injects formic acid into the skin. The effect of an acid can be neutralized by using basic medicines such as baking soda (sodium bicarbonate) or calamine solution which contains zinc carbonate. To treat wasp stings. Wasp sting is basic in nature. Vinegar (acetic acid) is used to cure wasp stings. Some people use mango pickles to cure wasp stings.

 

To treat acidic effluents

 

Effluents from the electroplating industries contain acids. They are treated by adding lime to them in-order to neutralize them.

 

To treat acidic soil

 

Acidic soil has poor fertility. Plants do not grow well in acidic soil. So in order to promote better fertility of the soil, Acidic soil is treated with quick lime (calcium oxide) or slaked lime (calcium hydroxide), or limestone (calcium carbonate) to neutralize its acidity.

 

To treat basic soil

 

Basic soil can be treated by using a compost of rotting vegetables and leaves. Organic matter releases acids which neutralizes the basic nature of the soil.

 

To treat tooth decay

 

Decaying food particles in our teeth produce acids and cause tooth decay. Toothpaste is basic in nature. Using toothpaste during brushing help to neutralize acids.

 

Read More-Acids and Bases: Definition, Properties, Uses, and Examples