Which of the following pairs of compounds can be used to illustrate the law of multiple proportion?

a) NH3 and NH4Cl
b) ZnO2 and ZnCl2
c) H2O and HCl
d) NO and NO2

Could you also briefly explain why, please. Thank you.

2 answers

NO, and NO2. Law of Multiple Proportion: when two elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.
notice the subscripts on the O atom, small whole numbers...
Thank you. :)