Types and Chemical Properties of Acids

Types of Acids

Acids can be classified as Organic Acids and Mineral Acids
The acids present in plant materials and animals are called organic acids
Example Acetic acid (or Ethanoic acid), Citric acid, Lactic acid, Tartaric acid, Oxalic acid and Formic acid (or Methanoic acid).
The acids prepared from the minerals of the earth are called mineral acids. Mineral acids are man made acids.
Hydrochloric acid, Sulphuric acid and Nitric acid. Concentrated mineral acids are very dangerous.
Question :Why the dilution of a concentrated acid should always be done by adding concentrated acid to water gradually with stirring and not by adding water to concentrated acid.
Answer When a concentrated acid is added to water for preparing a dilute acid, then the heat is evolved gradually, and easily absorbed by the large amount of water (to which acid is being added).
If, however, water is added to concentrated acid to dilute it, then a large amount of heat is evolved at once.
This heat changes some of the water to steam explosively which can splash the acid on our face or clothes and cause acid burns and can even break the glass.

Only hydrogen gas burns making a ‘pop’ sound.
This shows that hydrogen gas is evolved in the reaction of dilute sulphuric acid with zinc metal (taken in the form of zinc granules).
Acids react with metal carbonates (and metal hydrogencarbonates) to form carbon dioxide gas
Metal carbonate + Acid — Salt + Carbon dioxide + Water
Metal hydrogen carbonate + Acid — Salt + Carbon dioxide + Water
When dilute hydrochloric acid reacts with sodium carbonate, then sodium chloride, carbon dioxide and water are formed

The carbon dioxide gas is formed in the form of brisk effervescence (the rapid escape of small bubbles of gas from the liquid).
When dilute hydrochloric acid reacts with sodium hydrogen carbonate, then sodium chloride, carbon dioxide and water are formed

Calcium carbonate (White ppt.) Makes Lime Water Milky
On passing excess Carbon Dioxide white precipitate formed first dissolves due to the formation of a soluble salt calcium hydrogencarbonate, and the solution becomes clear again

limestone, marble and chalk are the different forms of the same chemical compound ‘calcium carbonate’. Even the egg-shells are made of calcium carbonate.

Acids react with bases (or alkalis) to form salt and water
the reaction between an acid and a base to form salt and water is called a neutralisation reaction
Base + Acid → Salt + Water