Crystallization is used to purify: MCQ with Answer and Explanation

Explanation:
Sulphuric acid (H₂SO₄) is known as the 'King of Chemicals' because of its extensive use in various industries, including fertilizers, dyes, detergents, and petroleum refining. Its production is often considered an indicator of a country's industrial strength and economic development.

Explanation:
John Dalton put forward the atomic theory in 1808, proposing that matter is made of indivisible atoms, atoms of same element are identical, and compounds are combinations of atoms. Electron was discovered by J.J. Thomson, periodic table by Mendeleev, neutron by Chadwick.

Explanation:
Rusting is a chemical change because iron reacts with atmospheric oxygen and moisture to form hydrated iron(III) oxide. This new compound possesses entirely different chemical properties from the original iron. The process involves the formation of new chemical bonds and cannot be easily reversed by simple physical methods.