State and explain law of definite proportions

Explanation

Law of Definite or Constant Proportions. Law of definite proportions states that, "In a pure chemical compound (or substance) the same elements are always present in definite proportion by mass This law is known as law of constant proportion or law of definite proportions.
For example, the ratio of the mass of hydrogen to the mass of oxygen is always 1 : 8 in pure water obtained from different sources. If 99 g of water is decomposed by passing electric current through it, then 11 g of hydrogen and 88 g of oxygen are always produced.
If 10g of hydrogen is burnt in 16g of oxygen, then 18g of water is formed and 8g of hydrogen remains as unreacted.
From the example discussed above, it is clear that ratio of mass of hydrogen to that of oxygen in water is always the same that is 1 : 8.
Similarly, pure carbon dioxide `(CO_(2))` obtained from different sources contains carbon and oxygen in the ratio of the 3 : 8 by mass.