Acid Base & Salt - Class 10th Science
What is an Acid?
Taste of foods makes our life tasty. Every food we eat has some taste. Those tastes are sour, sweet or salty. Some food items have bitter taste because of base present in them. Cold drinks taste slightly bitter because of presence of base in them.
Foods give these tastes because of presence of acid, salt, sweet or base in them.
Acids
Acids are sour in taste. Food items having acids are sour in taste.
Example:
Lemon, curd, tamarind, curd, unripe fruits etc. are some most common food items that are used in households. As these items contain acids, hence these are sour in taste.
Chemical substances that are detected commonly by their sour taste are called ACIDS.
Types of Acids:
On the basis of occurrence Acid can be divided into two types: these are Natural acid and Mineral acid
Natural Acid or Organic Acid:
Acids that are obtained from natural sources such as plants, animal etc. are called natural acids. Natural acids are also called Organic Acids.
Example:
Citric acid, acetic acid, lactic acid, tartaric acid, oxalic acid, formic acid, etc.
Sources of some of the natural acids:
Citric acid: Found in lemon, orange, and in most of the citrus fruits.
Acetic acid (Ethanoic acid): Found in vinegar.
Tartaric acid: Found in Tamarind
Oxalic acid: Found in tomato
Lactic acid: Found in sour milk, curd, etc.
Formic acid: Found in ant sting, nettle sting
Ascorbic acid: Found in guava, amla, etc.
Mineral Acids or Synthetic Acids:
Acids that are prepared from minerals are known as mineral acid.
Example: Hydrochloric acid, Sulphuric acid and Nitric acid are the most common mineral acids.
As mineral acids are prepared in laboratories thus, mineral acids are also known as man-made or synthetic acids or inorganic acids.
Strong and Weak Acids:
Acid can be strong or weak.
Strong acids:
All mineral acids are strong acids except carbonic acid. For example: sulphuric acid, hydrochloric acid, nitric acid, phosphoric acid.
Weak acids:
All organic acids i.e. naturally occurring acids are weak acids. For example: tartaric acid, oxalic acid, formic acid, acetic acid, etc.
Concentrated and Dilute Acid
Concentrated Acid:
Aqueous solution in which volume of constituents of acid is maximum is called caoncentrated acid.
Concentration is defined as the abundance of a constituent divided by the total volume of a mixture.
Concentration of acid decreases with decrease the volume of constituents of acid in its aqueous solution.
Dilute Acid:
Aqueous solution of acid in which volume of constituents is not maximum is called dilute acid.
Dilution of acid increases with increase in solvent.
How to dilute an acid?
Acid can be diluted by mixing of acid into water. Dilution of acid is an exothermic process.
Caution: Always acid is slowly mixed in water to dilute the acid. Never mix water into acid to dilute. Mixing of water into acid can be very dangerous.
Properties of Acids:
- Acid tastes sour.
- Acid turns blue litmus to red.
- Dilution of acid is exothermic.
- Acids are good conductor of electricity in the solution.
- Acid forms hydrogen gas when reacts with metal.
- Acid forms salt and water when reacts with base.