Chemical Properties of Acid:

Concentrated acid: It is a type of acid solution in which amount of acid is more.

Dilute acid:  It is type of acid solution in which amount of acid is less.

example: In test tube A:4mL of HCl is dissolved in 10mL of water,

                In test tube B: 8mL of HCl is dissolved in 10mL of water.

Acid present in test tube B is more concentrated.

Chemical properties of acid:

(i) Reaction of acids with metal: Acids give hydrogen gas along with respective salt when they react with a metal.
Metal + Acid → Salt + Hydrogen
Examples:
Hydrogen gas and zinc chloride are formed when hydrochloric acid reacts with zinc metal.

Hydrogen gas and sodium sulphate are formed when sulphuric acid reacts with sodium metal.

Test For Hydrogen Gas: The gas evolved after reaction of acid with metal can be tested by bringing a lighted candle near it. If the gas bums with a pop sound, then it confirms the evolution of hydrogen gas. Burning with pop sound is the characteristic test for hydrogen gas.

(ii) Reaction of acids with metal carbonate: Acids give carbon dioxide gas and respective salts along with water when they react with metal carbonates.
Metal carbonate + Acid → Salt + Carbon dioxide + Water
Examples:
Hydrochloric acid gives carbon dioxide gas, sodium chloride along with water when reacts with sodium carbonate.

Sulphuric acid gives calcium sulphate, carbon dioxide gas, calcium sulphate and water when it reacts with calcium carbonate

Nitric acid gives sodium nitrate, water and carbon dioxide gas when it reacts with sodium carbonate.

(iii) Reaction of acid with hydrogen carbonates (bicarbonates): Acids give carbon dioxide gas, respective salt and water when they react with metal hydrogen carbonate.
Acid + Metal hydrogen carbonate → Salt + Carbon dioxide + Water
Example:
Sulphuric acid gives sodium sulphate, Carbon dioxide gas and water when it reacts with sodium bicarbonate.

Test For Evolution of Carbon Dioxide Gas: Carbon dioxide turns lime water milky when passed through it. This is the characteristic test for carbon dioxide gas.
The gas evolved because of reaction of the acid with metal carbonate or metal hydrogen carbonate turns lime water milky. This shows that the gas is carbon dioxide gas. This happens because of the formation of a white precipitate of calcium carbonate.

But when excess of carbon dioxide is passed through lime water, it makes milky colour of lime water disappear. This happens because of formation of calcium hydrogen carbonate. As calcium hydrogen carbonate is soluble in water, thus, the milky colour of solution mixture disappears.

(iv) Effect of pH paper: When a drop of acid is put on the pH paper with the help of dropper, the colorpf pH paprturns to pink.

Common in Acids: Acids give hydrogen gas when they react with metal. This shows that all acids contains hydrogen. For example; Hydrochloric acid (HCl), sulphuric acid (H2SO4), nitric acid (HNO3), etc.
When an acid is dissolved in water, it dissociates hydrogen. The dissociation of hydrogen ion in aqueous solution is the common property in all acids. Because of the dissociation of hydrogen ion in aqueous solution, an acid shows acidic behaviour.
Examples:
Hydrochloric acid (HCl) gives hydrogen ion (H+) and chloride ion (Cl–) when it is dissolved in water.

Acetic acid (CH3COOH) gives acetate ion (CH3COO–) and hydrogen ion (H+).