Which of the given molecules disobeys the law of definite proportion

 

Solution:

Concept: The ratio of elements in non-stoichiometric compounds changes from sample to sample. Thus, these compounds are found to be an exception to the law of constant proportions. 

Samples of elements that vary in their isotopic composition can also disobey the law of definite proportions since the masses of two different isotopes of an element are different. 

Natural polymers also disobey the law of definite proportions.