Question 16: (i) State the various postulates of Dalton's atomic theory of matter.
(ii) Which postulates of Dalton's atomic theory can explain the law of conservation of mass?
​(iii) Which postulate of Dalton's atomic theory can explain the law of constant proportions?

Answer: (a) Postulates of Dalton's atomic theory:
(i) All matter is made up of very tiny indivisible particles called atoms.
(ii) All the atoms of a given element are identical in mass and chemical properties whereas those of different elements have different masses and chemical properties.
(iii) Atoms of different elements combine in a fixed whole number ratio to form compounds.
(iv) Chemical reactions involve reorganization of atoms. Atoms can neither be created nor be destroyed.

(b) Atoms can neither be created nor be destroyed in a chemical reaction, it can be changed from one form to another. So, this explains the law of conservation of mass.


(c) Atoms of different elements combine in a fixed whole number ratio to form compounds. So, this explains the law of constant proportions.