Question

3 elements and compounds (continued)

1. explain how the law of definite proportions applies to compounds.

Explanation:

The law of definite proportions states that a compound always contains the same elements in exactly the same proportions by mass. For example, water ($H_2O$) always has hydrogen and oxygen in a ratio of 1:8 by mass. No matter how water is obtained - from a river, by melting ice, or through a chemical reaction - this proportion remains constant. This is because the atoms of the elements in a compound combine in fixed - whole - number ratios to form molecules.

Answer:

A compound always contains the same elements in the same proportions by mass due to the fixed whole - number ratios in which atoms combine to form its molecules.