How did Dalton Atomic Theory explain the law of definite proportions?
Dalton's atomic theory consisted of several postulates.
All matter consists of indivisible particles called atoms.
Atoms of the same element are similar in shape and mass, but differ from the atoms of other elements.
Atoms cannot be created or destroyed.
Atoms of different elements may combine with each other in a fixed, simple, whole number ratio to form compound atoms.
Atoms of same element can combine in more than one ratio to form two or more compounds.
Atoms are the smallest unit of matter that can take part in a chemical reaction.
The law of definite proportions states that a chemical compound always contains exactly the same proportion of elements by mass.
For example, all samples of the compound carbon monoxide contain 42.88 % carbon and 57.12 % oxygen by mass.
The atomic theory explains the law of definite proportions:
Dalton proposed that the smallest particle of carbon monoxide was a molecule. This molecule consisted of one carbon atom and one oxygen atom.
If all oxygen atoms had a mass about 1.33 times that of carbon atoms, carbon monoxide would have exactly the above composition.