Law of constant proportions:
This law was first stated by Proust in 1797. According to the law “In a chemical substance the elements are always present in definite proportions by mass”.” e.g. the ratio of hydrogen and oxygen in pure water is always 1: 8 by weight. So if we decompose 9g of water we will obtain 1g of hydrogen and 8g of oxygen.
law of definite proportions:
According to Dalton’s atomic theory, all matter, whether an element, a compound or a mixture is composed of small particles called atoms. The postulates of this theory may be stated as follows:
- All matter is made of very tiny particles called atoms, which participate in chemical reactions.
- Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction.
- Atoms of a given element are identical in mass and chemical properties.
- Atoms of different elements have different masses and chemical properties.
- Atoms combine in the ratio of small whole numbers to form compounds.
- The relative number and kinds of atoms are constant in a given compound.
Shaalaa.com | Atoms and Molecules (Dalton Atomic Theory)
When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combinations will govern your answer?