Q.State the law of definite proportion.

The law of definite proportions (Proust's law) states that a given compound always contains exactly the same proportion of elements by mass, no matter its source.

Proposed by the French chemist Joseph Proust in 1799, the law of definite proportions (also called the law of constant composition) states that a given compound always contains exactly the same proportion of elements by mass. For example, pure water, whether obtained from a river, a lake, or prepared synthetically by burning hydrogen in oxygen, always contains hydrogen and oxygen combined in the same fixed mass ratio of 1:8 (a mole ratio of 2:1). This law was fundamental in establishing that compounds have a fix …

The law of definite proportions states that a pure compound always has the same elements in the same fixed mass ratio, regardless of source.

Proposed by the French chemist Joseph Proust in 1799, the law of definite proportions (also called the law of constant composition) states: 'A given compound always contains exactly the same proportion of elements by weight (mass).' For example, pure water (H2O), whether obtained from a river, from rain, or prepared synthetically by burning hydrogen in oxygen, always contains hydrogen and oxygen combined in the fixed mass ratio of 1:8 (i.e. 11.1% hydrogen and 88.9% oxygen by mass). This law was central to establishing Dalton's atomic theory, since a fixed combining ratio by mass is nat …