Acids Bases And Salts
Introduction
- You all know that lemon, tomato, oranges tastes sour. You also know that all of them contain citric acid. This is the best natural example to prove that acids are sour in taste.
- On the other hand you all know that increased amount of baking soda makes the cake taste bitter. This is because baking soda is a base and hence tastes bitter.
- So we conclude that acids can be easily pointed out by their sourness whereas bases can be easily pointed out by their bitterness.
Acids and bases
- The substances that taste sour are called acid and their nature is acidic. The term acid is derived from a Latin word acere which means sour. Examples of acidic substances are Curd containing lactic acid, lemon juice and tomato containing citric acid, and vinegar containing acetic acid.
- The substances that taste bitter are called base and their nature is basic. They are slippery to touch. Example: baking soda containing sodium hydrogen carbonate, Milk of magnesia, Soaps, Lime water containing calcium hydroxide, Household cleaners.
Indicators
- Substances that are used to indicate whether a substance is acid or a base are known as indicators. They change their color on addition of a solution containing an acidic or a basic substance.
- In our day to day life we get to see many examples where indicators change their color when comes in contact with acid or base.
- For instance, while washing clothes if a shirt having a spot of curry turns to reddish brown when comes in contact with the detergent soap but soon disappears when washed thoroughly. This is due to the presence of base in detergent that changes the color of the turmeric indicator.
- There are several types of indicators used in our day to day life. Some of them are litmus paper or solution, phenolphthalein, China rose.
Litmus Test
- Litmus is the most commonly used natural indicator available as strips of paper or solution. It is extracted from lichens. It turns to red on addition of an acidic solution and turns blue on addition of a basic solution.
China rose indicator
- Another natural indicator used to determine whether a substance is acidic or basic is China rose which turns acidic solutions to dark pink or magenta color and basic solutions to green color.
Phenolphthalein
- Phenolphthalein is another indicator giving a pink color in case of basic solution and remaining colorless in case of acidic solution.
Neutralization
- The reaction between an acid and a base to give a salt and water is known as a neutralization reaction. Acids and bases react with each other to nullify the effect of each other.
- Let us consider a simple reaction. Take a sample of NaOH which is a base and add drops of dilute HCl.
- The reaction will be as follows:
- Therefore while suffering from acidity it is prescribed to take antacid which are bitter in taste i.e. they are base. And on entering the body the base neutralizes the excess acid released into the stomach and converts it into salt and water.
Neutralisation in everyday life
Indigestion
- The stomach contains hydrochloric acid that helps to digest food. But presence of too much acid in the stomach may lead to indigestion that can be relieved by taking an antacid such as milk of magnesia containing magnesium hydroxide and effective in neutralizing the effect of excessive acid.
Ant bite
- Ant bites inject formic acid present in its sting, into our body. The effect of the formic acid injected into our body can be nullified by rubbing moist baking soda i.e. sodium hydrogen carbonate or calamine solution, containing zinc carbonate.
Soil treatment
- Excessive use of chemical fertilizers results in increased acidity of the soil which is not at all suitable for proper plant growth. Plants cannot even grow well when the soil is too basic.
- Too much acidity of soil is neutralized using bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide). Whereas too much basicity of soil is neutralized by using Organic matter that releases acids and thereby neutralizes the basic nature of the soil.
Factory wastes
- The wastes excreted out of factories are highly acidic and causes threat to the survival of the marine ecosystem. Release of these acidic wastes into the water bodies, kills fish and other organisms. Due to which the factory wastes are properly neutralized by adding basic substances.
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